My guess is that (even with everything virtualizing) 5G in 2020 will be at least as expensive as 4G now, probably still much earlier in the development and cost-reduction curve, and limping along with an old system will be more of a drag on their economy than upgrading. Also, a big part of the cost of any of those systems has been spectrum, which is a problem when a US or EU telcos have to be the highest bidder in a government auction that's trying to maximize revenue; a government-run telco in Cuba doesn't have that artificial expense.
As far as I can tell from the documentation, FreeBSD isn't usable for as a production hypervisor unless you're willing to make a large investment in supporting bhyve (I don't count VirtualBox as production - it's fine for development, but too slow for production.) But how is it as a client on top of KVM or VMware? Can you run a usable system without burning too much disk or memory, compared to Red Hat or Ubuntu?
California's been burning through groundwater supplies faster than rainfall replenishes them even in the average-rainfall years. It's unsustainable in good times, much less in crisis droughts like the current one.
It's not like that's not a problem other places around the US or the world; look at how the MidWest and Texas are doing.
Of course we should require cities to pay to build highly expensive desalination plants and burn greenhouse gasses to power them so that we can continue to provide agribusiness with cheap water using socialist-built water projects so they can continue to make a profit growing water-intensive crops in semi-desert areas. After all, how else are cotton farmers going to get subsidized for growing something other than cotton and happy cows in China going to get alfalfa grown in California, not even counting the rest of the crops that, even in average-rainfall years, were using up California's ground-water faster than rain was restocking it?
There may be a bit of residual market for 3G (or less likely, GSM), but they'd be much better off doing 4G than waiting five years for some magic 5G, or expecting enough Wifi and internet to be available to replace the cellular-standards market. US carriers are retiring 3G as fast as they can, going to LTE, because they get more efficient use of the bandwidth, as well as faster data and the possibility of VoLTE. The real issue is partly the rate at which cheap phones from China are adopting 4G, plus the fraction of tourists from areas that are still on 3G.
There's a good chance that it was already illegal, at least under FCC regs, for your town to forbid you to offer those services, based on the regs that applied to cable TV overbuilding; if they'd been willing to sell you a license but wanted an extortionate price for it, they probably would have been fine.
But yeah, I watched cable TV service evolve in New Jersey in the 80s, and it was very clear that the decision about who got franchises wasn't based on who was the most forward-thinking about visionary telecommunications services for the citizens, it was about whose brother-in-law got the paving contract and how much the kickbacks for construction were going to be. And in San Francisco in the 90s and 00s, a lot of it was also about how many of the kinds of channels the city council members liked would be carried, and how many public-access channels would be available for them to make speeches on, as well as about tearing up streets. No surprise your town was as hostile about Internet service.
Electric company rights-of-way over long distances are easy to reuse by adding fiber. Rights-of-way to the block are usually not too hard to reuse, depending on how the construction's done and what the rules are for using easements. Digging up streets always costs a lot - if you don't have conduit, and the transmission's not on poles, it's not likely to be a winning proposition, but if you have those, it's not bad.
Rights-of-way to your house are a lot tougher - if they have to run fiber, as opposed to radio-down-the-block, it may not be too bad in places that still have overhead electricity on poles, but is a lot more expensive and difficult if you've got underground services.
It also turns out that the easements that electric companies have may not be usable for other kinds of utility services; cable TV companies ran into this problem when they wanted to rent direct fiber to businesses in a lot of places. Transmitting data signals over the same facilities as the TV was ok, but running separate fibers rented out for other purposes hit all sorts of regulatory bogosity. Maybe that's been fixed since the 90s and early 00s, but it was one of the reasons AT&T ended up selling off Comcast after they'd bought it, because it was much harder to use the right-of-way profitably.
Double the range, quadruple the number of users in range. That's both good and bad; if you're building a service for which a low bandwidth per user is ok, like messaging or voice telephony or email, it's great; if you're building a service that needs high bandwidth, like unicast video downloading, it's bad. If you've got an application that transmits high bandwidth to lots of users simultaneously, it's great (oh, wait, that's called Television, and this bandwidth is available because we like the Internet and cable better:-)
Personally, I think making it available to the public is a great idea - we can probably invent far more things to do with it than small number of licensed carriers, for who it's just a percentage increase in potential number of subscribers.
The big issues for them, if I understand the press releases, is partly to get access to more and better content than U-Verse can afford with its market alone, partly to get access to a lot more subscribers (who might be willing to buy other services), particularly in Verizon and CenturyLink parts of the US, and partly to get more access to the Mexican market.
I don't think it means what the FBI is claiming it means, and I think they know it doesn't mean that either. Leaving aside whether quoting somebody is support or opposition, it's clearly speech, not material support. You're not paying money for that Tweet, and there aren't any new electrons created to propagate it. If anything, the FBI ought to be charged for obstructing justice in this case.
Venom means the animal can use it to attack you, as opposed to being passively poisonous if you eat it, which can still be a useful defense mechanism for a species, if not for the animal that gets eaten. But an animal that spits something poisonous into your eyes or nose would still be venomous even if it wasn't biting or stabbing you to inject it, as would an animal that bites or scratches you and then spits poison out of its mouth, even if it doesn't have fangs.
Biologically, we're not venomous (though bites or scratches inflicted by humans can get infected.) But somebody with a venomous attitude toward you may try to poison you, or kill you with a blunt instrument or sharp object.
It's venom if the animal can use it to attack you, but an animal (or plant or mineral) can be poisonous without being venomous. If a traditional hunter wants something to poison an animal or a traditional warrior wants something to poison an enemy with, in either case by using a dart or arrow or knife coated with the poison, they could use venom from a venomous animal, or they could use some other poison that's available. (Those poisons have a partial overlap with the poisons an assassin or a bad cook could use to poison your food with; some poisons need to be eaten to be harmful, some poisons need to be injected but are rendered mostly harmless by the digestive system.)
Venom is something the animal can use to attack you with; poison is something that affects you if you attack the animal (or eat or breathe or otherwise get the animal, plant, or mineral material into your body.)
Leave aside how you get the venom out of the frog (that's an exercise in applied bio-technology), poisoned darts and arrows are a technique for injecting it into a victim. Works just about as well if it's a venom that the original animal could inject into you by itself, or a poison that normally would only get into your bloodstream if you ate the animal, snorted it, or got it on a cut in your skin. (There are some poisons that only affect you if you eat and digest them, but they're not the kind that would be useful as arrow poisons.)
I've tried wearing opaque masks to keep light from waking me up in the morning. Maybe a heavy-duty one like this would stay on better; the light-weight travel mask I've used tends to slip off (especially because it doesn't quite fit over my CPAP mask's straps), though it's some help.
And my cat doesn't sleep on my face; he prefers being on the pillow at the top of my head, or taking up the middle half of the bed.
Zeo used EEG to detect your brain activity related to sleep, and sound to wake you up. Any idea where to get new sensor pads? Mine have long worn out, so I'm just using the control box as a conventional alarm clock these days.
There have been several REM-detecting masks in the past that watch for eye movement or maybe electrical signals from the muscles near your eyes; my wife has one that one of the Stanford researchers made a decade or so ago (with 9-pin RS232 for download/settings:-) I didn't watch the video, but the text looks like that's what this device is doing.
Also, this uses light to wake you up. Sorry, I want noise as a backup. I did have an officemate once who was deaf, and used lights on a timer as his alarm clock, which occasionally gave him trouble when he was travelling, because of polarized-vs-nonpolarized plug differences between his timer and hotel electric sockets.
I haven't tried them - the nose-pillow types of CPAP mask work really well for me, though I suppose I should try picking up a pack of them for travel. They're basically a bandaid with valves that you stick on your nose at night, and while they're not going to take an average sleep-apnea patient from 40 down to 5 AHI, they might take you down to 10.
Also, if your CPAP is making loud noises when you take it off, see if your DME can adjust its settings for you. One of the standard brands of machines does about 10 seconds of air after you take it off to clean out the hoses, but maybe that's adjustable, depending on whether you're using a fixed or variable pressure setting. (I usually turn the machine off before taking off the mask, so the noise doesn't wake up my wife.)
The US wireless carrier may be selling the phones for disposable prices, but they're paying the manufacturer the real price (with highly negotiated discount rates and volume plans, I'm sure, but the manufacturer isn't selling them below cost.) I've got a Galaxy S4 Mini, because it was smaller than the newer phones they had on the market at the time, and I wanted a phone that would fit in my pocket. Probably should have gotten an Apple iPhone instead.
Back when my niece was a young teen, she and her school friends used Facebook, but would wipe out their profiles every year and build new ones with new pseudonyms. Protected their privacy that way, and automatically fixes the "erase dumb stuff you said as a kid" problems.
What a hopeless article. Yes, real quantum computing would be cool, and D-Wave has been doing quantum-y things with investor money for a decade or so, and scientists have developed improved more standard kinds of quantum computers to the point that they can now factor 21, surpassing the record of factoring 15 that held for a few years, and maybe sometime in the future quantum computers will be as far advanced beyond that as today's rockets are beyond the ones Goddard had on paper a century ago or his early flying models 90 years ago, or maybe not (or maybe both at once, because YOU CAN DO THAT with quantum.)
But like most articles about quantum stuff in the popular press, and 99.9999% of content about it in the New Age business, it follows the paradigm of
1. I don't understand quantum! 2. I can imagine really cool things that I don't understand how to make! 3. ???? 4. PROFIT! , err, Therefore, quantum is how to make really cool things I want! QED!
Quantum physics isn't a Simple Matter Of Engineering like rocketry (and there are reasons for the phrase "Rocket Scientist" - rocketry's also more than just a S.M.o.E, no matter what you remember from those Heinlein stories you read as a kid about building spaceships in your back yard.) Mathematics and physics breakthroughs don't just happen because you really really want them to or because you pour lots of money into the engineering (though especially for the physics, that really helps.)
And yes, D-Wave might be on to something, or they might be pursuing a dead end, and we'd learn valuable things by helping them do either one, if they publish enough detail about their work, and maybe they can build quantumy computers that are useful for real-world problems even if you can't use them to run Shor's Algorithm to crack factoring-based crypto. But just because rocketry was at sort of a cusp a century ago, and lots of other technologies have gone from "not ready/usable yet" to "useful" that doesn't mean that quantum computing is one of them; lots of other technologies have gone from "not ready/usable yet" to "old obsolete dead ends."
And there are a bunch of similar applications for which you might want to be able to verify that the mail's only going where it should, and that it won't stick around as a legal record longer than you want it to.
This approach to special-handling-required email is pretty common - if the recipient has the right software (client / app / browser extension / whatever), their email client can read it directly, otherwise they have to use a web link to the provider's server. The more secure and scalable versions store only keys of some kind on the server, and include the encoded or encrypted message in the email, the simpler but less scalable and less secure ones keep it on the server and just include a link in the email.
Disappearing Inc did that back in 2000 for a self-destructing email application, and I've seen similar things for encrypted mail (e.g. Voltage Secure Mail) and other applications (often marketed as "Data Loss Prevention" or whatever), mostly for corporate users.
And yeah, if I get email from some random stranger saying "You've received a Whiffly-Mail Message, Click Here to Download", it's going in the spam bucket, but if I get it from somebody I regularly deal with I'm fairly likely to open it. Can't be much worse than opening a Microsoft Word document from a stranger. And of course, if it's from Paypal or SomeBigBank or Microsoft Technical Support, it gets junked as well.
Yes, you could implement it by storing the message contents on a server, but the non-LOL version that Disappearing Inc implemented back in ~2000 sent the encrypted message to the recipient, and only kept the key on the server. If you had a client at the recipient's end, it would fetch the key, otherwise you'd paste it into an SSL form on a web browser that would decrypt it. DI would delete the key after whatever business rules you liked (typically N days, or read-N-times, or "recipient clicks Delete", or sender clicks "Ooops.", etc.)
Does this keep the whole message on the server or just the keys? Hopefully the latter, because it's more secure, but I don't know.
Back in 2000, a company called Disappearing Inc. made a presentation to the Bay Area Cypherpunks meeting about their product, which was pretty similar except that back then most people used real email clients instead of webmail. When the guy walked in, and we were expecting him to be pushing some kind of snake oil, he started out by saying that their threat model was to let cooperating people have some guarantee that their email would go away when they wanted it to, not to keep uncooperative people from doing that because you just can't stop screenshots / cameras / sender saving a copy / etc. and anybody trying to sell you that is selling snake oil. And suddenly he had a friendly audience, instead of one that was going to beat him up, because he'd defined a problem that could be believably solved, which was cool.
So the trick is that the file's in an encrypted format, and Disappearing Inc's server keeps the keys and a delete date for them, and if the sender and recipient are both using their product, the reader program/plugin/etc. fetches the key from DI's server; if not, you drop the file into an SSL-encrypted web form on DI which decrypts it for you. When the delete date hits (or earlier, if the file's set for read-only-once), DI deletes their copy of the key, so the recipient's mail box now has an encrypted binary blob file with no decryption key. Yes, if the server gets compromised, it's all toast. Yes, if the recipient's email client or browser is compromised at the time they read it, it's all toast. But if nobody's trying to subpoena or crack the message until after the key's deleted, then it's too late to recover old messages, though you can always try to attack new ones.
It was a nice system, and they stayed in business a couple of years before getting bought by somebody who got bought by somebody and disappearing into dead-dot-com-space. Similar systems have been sold by various other companies, often under category names like "Data Loss Protection".
If you wanted to do a "no forwarding" version, you'd do it by setting rules on who could access it, whether by IP address or some ID in the reader plugin or delete-after-one-read or whatever.
Slashdot Mirror
My guess is that (even with everything virtualizing) 5G in 2020 will be at least as expensive as 4G now, probably still much earlier in the development and cost-reduction curve, and limping along with an old system will be more of a drag on their economy than upgrading. Also, a big part of the cost of any of those systems has been spectrum, which is a problem when a US or EU telcos have to be the highest bidder in a government auction that's trying to maximize revenue; a government-run telco in Cuba doesn't have that artificial expense.
As far as I can tell from the documentation, FreeBSD isn't usable for as a production hypervisor unless you're willing to make a large investment in supporting bhyve (I don't count VirtualBox as production - it's fine for development, but too slow for production.) But how is it as a client on top of KVM or VMware? Can you run a usable system without burning too much disk or memory, compared to Red Hat or Ubuntu?
California's been burning through groundwater supplies faster than rainfall replenishes them even in the average-rainfall years. It's unsustainable in good times, much less in crisis droughts like the current one.
It's not like that's not a problem other places around the US or the world; look at how the MidWest and Texas are doing.
Of course we should require cities to pay to build highly expensive desalination plants and burn greenhouse gasses to power them so that we can continue to provide agribusiness with cheap water using socialist-built water projects so they can continue to make a profit growing water-intensive crops in semi-desert areas. After all, how else are cotton farmers going to get subsidized for growing something other than cotton and happy cows in China going to get alfalfa grown in California, not even counting the rest of the crops that, even in average-rainfall years, were using up California's ground-water faster than rain was restocking it?
There may be a bit of residual market for 3G (or less likely, GSM), but they'd be much better off doing 4G than waiting five years for some magic 5G, or expecting enough Wifi and internet to be available to replace the cellular-standards market. US carriers are retiring 3G as fast as they can, going to LTE, because they get more efficient use of the bandwidth, as well as faster data and the possibility of VoLTE. The real issue is partly the rate at which cheap phones from China are adopting 4G, plus the fraction of tourists from areas that are still on 3G.
There's a good chance that it was already illegal, at least under FCC regs, for your town to forbid you to offer those services, based on the regs that applied to cable TV overbuilding; if they'd been willing to sell you a license but wanted an extortionate price for it, they probably would have been fine.
But yeah, I watched cable TV service evolve in New Jersey in the 80s, and it was very clear that the decision about who got franchises wasn't based on who was the most forward-thinking about visionary telecommunications services for the citizens, it was about whose brother-in-law got the paving contract and how much the kickbacks for construction were going to be. And in San Francisco in the 90s and 00s, a lot of it was also about how many of the kinds of channels the city council members liked would be carried, and how many public-access channels would be available for them to make speeches on, as well as about tearing up streets. No surprise your town was as hostile about Internet service.
Electric company rights-of-way over long distances are easy to reuse by adding fiber. Rights-of-way to the block are usually not too hard to reuse, depending on how the construction's done and what the rules are for using easements. Digging up streets always costs a lot - if you don't have conduit, and the transmission's not on poles, it's not likely to be a winning proposition, but if you have those, it's not bad.
Rights-of-way to your house are a lot tougher - if they have to run fiber, as opposed to radio-down-the-block, it may not be too bad in places that still have overhead electricity on poles, but is a lot more expensive and difficult if you've got underground services.
It also turns out that the easements that electric companies have may not be usable for other kinds of utility services; cable TV companies ran into this problem when they wanted to rent direct fiber to businesses in a lot of places. Transmitting data signals over the same facilities as the TV was ok, but running separate fibers rented out for other purposes hit all sorts of regulatory bogosity. Maybe that's been fixed since the 90s and early 00s, but it was one of the reasons AT&T ended up selling off Comcast after they'd bought it, because it was much harder to use the right-of-way profitably.
Double the range, quadruple the number of users in range. That's both good and bad; if you're building a service for which a low bandwidth per user is ok, like messaging or voice telephony or email, it's great; if you're building a service that needs high bandwidth, like unicast video downloading, it's bad. If you've got an application that transmits high bandwidth to lots of users simultaneously, it's great (oh, wait, that's called Television, and this bandwidth is available because we like the Internet and cable better :-)
Personally, I think making it available to the public is a great idea - we can probably invent far more things to do with it than small number of licensed carriers, for who it's just a percentage increase in potential number of subscribers.
The big issues for them, if I understand the press releases, is partly to get access to more and better content than U-Verse can afford with its market alone, partly to get access to a lot more subscribers (who might be willing to buy other services), particularly in Verizon and CenturyLink parts of the US, and partly to get more access to the Mexican market.
I don't think it means what the FBI is claiming it means, and I think they know it doesn't mean that either. Leaving aside whether quoting somebody is support or opposition, it's clearly speech, not material support. You're not paying money for that Tweet, and there aren't any new electrons created to propagate it. If anything, the FBI ought to be charged for obstructing justice in this case.
Venom means the animal can use it to attack you, as opposed to being passively poisonous if you eat it, which can still be a useful defense mechanism for a species, if not for the animal that gets eaten. But an animal that spits something poisonous into your eyes or nose would still be venomous even if it wasn't biting or stabbing you to inject it, as would an animal that bites or scratches you and then spits poison out of its mouth, even if it doesn't have fangs.
Biologically, we're not venomous (though bites or scratches inflicted by humans can get infected.) But somebody with a venomous attitude toward you may try to poison you, or kill you with a blunt instrument or sharp object.
It's venom if the animal can use it to attack you, but an animal (or plant or mineral) can be poisonous without being venomous. If a traditional hunter wants something to poison an animal or a traditional warrior wants something to poison an enemy with, in either case by using a dart or arrow or knife coated with the poison, they could use venom from a venomous animal, or they could use some other poison that's available. (Those poisons have a partial overlap with the poisons an assassin or a bad cook could use to poison your food with; some poisons need to be eaten to be harmful, some poisons need to be injected but are rendered mostly harmless by the digestive system.)
Venom is something the animal can use to attack you with; poison is something that affects you if you attack the animal (or eat or breathe or otherwise get the animal, plant, or mineral material into your body.)
Leave aside how you get the venom out of the frog (that's an exercise in applied bio-technology), poisoned darts and arrows are a technique for injecting it into a victim. Works just about as well if it's a venom that the original animal could inject into you by itself, or a poison that normally would only get into your bloodstream if you ate the animal, snorted it, or got it on a cut in your skin. (There are some poisons that only affect you if you eat and digest them, but they're not the kind that would be useful as arrow poisons.)
I've tried wearing opaque masks to keep light from waking me up in the morning. Maybe a heavy-duty one like this would stay on better; the light-weight travel mask I've used tends to slip off (especially because it doesn't quite fit over my CPAP mask's straps), though it's some help.
And my cat doesn't sleep on my face; he prefers being on the pillow at the top of my head, or taking up the middle half of the bed.
Zeo used EEG to detect your brain activity related to sleep, and sound to wake you up. Any idea where to get new sensor pads? Mine have long worn out, so I'm just using the control box as a conventional alarm clock these days.
There have been several REM-detecting masks in the past that watch for eye movement or maybe electrical signals from the muscles near your eyes; my wife has one that one of the Stanford researchers made a decade or so ago (with 9-pin RS232 for download/settings :-) I didn't watch the video, but the text looks like that's what this device is doing.
Also, this uses light to wake you up. Sorry, I want noise as a backup. I did have an officemate once who was deaf, and used lights on a timer as his alarm clock, which occasionally gave him trouble when he was travelling, because of polarized-vs-nonpolarized plug differences between his timer and hotel electric sockets.
I haven't tried them - the nose-pillow types of CPAP mask work really well for me, though I suppose I should try picking up a pack of them for travel. They're basically a bandaid with valves that you stick on your nose at night, and while they're not going to take an average sleep-apnea patient from 40 down to 5 AHI, they might take you down to 10.
Also, if your CPAP is making loud noises when you take it off, see if your DME can adjust its settings for you. One of the standard brands of machines does about 10 seconds of air after you take it off to clean out the hoses, but maybe that's adjustable, depending on whether you're using a fixed or variable pressure setting. (I usually turn the machine off before taking off the mask, so the noise doesn't wake up my wife.)
The US wireless carrier may be selling the phones for disposable prices, but they're paying the manufacturer the real price (with highly negotiated discount rates and volume plans, I'm sure, but the manufacturer isn't selling them below cost.)
I've got a Galaxy S4 Mini, because it was smaller than the newer phones they had on the market at the time, and I wanted a phone that would fit in my pocket. Probably should have gotten an Apple iPhone instead.
Back when my niece was a young teen, she and her school friends used Facebook, but would wipe out their profiles every year and build new ones with new pseudonyms. Protected their privacy that way, and automatically fixes the "erase dumb stuff you said as a kid" problems.
What a hopeless article. Yes, real quantum computing would be cool, and D-Wave has been doing quantum-y things with investor money for a decade or so, and scientists have developed improved more standard kinds of quantum computers to the point that they can now factor 21, surpassing the record of factoring 15 that held for a few years, and maybe sometime in the future quantum computers will be as far advanced beyond that as today's rockets are beyond the ones Goddard had on paper a century ago or his early flying models 90 years ago, or maybe not (or maybe both at once, because YOU CAN DO THAT with quantum.)
But like most articles about quantum stuff in the popular press, and 99.9999% of content about it in the New Age business, it follows the paradigm of
Quantum physics isn't a Simple Matter Of Engineering like rocketry (and there are reasons for the phrase "Rocket Scientist" - rocketry's also more than just a S.M.o.E, no matter what you remember from those Heinlein stories you read as a kid about building spaceships in your back yard.) Mathematics and physics breakthroughs don't just happen because you really really want them to or because you pour lots of money into the engineering (though especially for the physics, that really helps.)
And yes, D-Wave might be on to something, or they might be pursuing a dead end, and we'd learn valuable things by helping them do either one, if they publish enough detail about their work, and maybe they can build quantumy computers that are useful for real-world problems even if you can't use them to run Shor's Algorithm to crack factoring-based crypto. But just because rocketry was at sort of a cusp a century ago, and lots of other technologies have gone from "not ready/usable yet" to "useful" that doesn't mean that quantum computing is one of them; lots of other technologies have gone from "not ready/usable yet" to "old obsolete dead ends."
And there are a bunch of similar applications for which you might want to be able to verify that the mail's only going where it should, and that it won't stick around as a legal record longer than you want it to.
This approach to special-handling-required email is pretty common - if the recipient has the right software (client / app / browser extension / whatever), their email client can read it directly, otherwise they have to use a web link to the provider's server. The more secure and scalable versions store only keys of some kind on the server, and include the encoded or encrypted message in the email, the simpler but less scalable and less secure ones keep it on the server and just include a link in the email.
Disappearing Inc did that back in 2000 for a self-destructing email application, and I've seen similar things for encrypted mail (e.g. Voltage Secure Mail) and other applications (often marketed as "Data Loss Prevention" or whatever), mostly for corporate users.
And yeah, if I get email from some random stranger saying "You've received a Whiffly-Mail Message, Click Here to Download", it's going in the spam bucket, but if I get it from somebody I regularly deal with I'm fairly likely to open it. Can't be much worse than opening a Microsoft Word document from a stranger. And of course, if it's from Paypal or SomeBigBank or Microsoft Technical Support, it gets junked as well.
Yes, you could implement it by storing the message contents on a server, but the non-LOL version that Disappearing Inc implemented back in ~2000 sent the encrypted message to the recipient, and only kept the key on the server. If you had a client at the recipient's end, it would fetch the key, otherwise you'd paste it into an SSL form on a web browser that would decrypt it. DI would delete the key after whatever business rules you liked (typically N days, or read-N-times, or "recipient clicks Delete", or sender clicks "Ooops.", etc.)
Does this keep the whole message on the server or just the keys? Hopefully the latter, because it's more secure, but I don't know.
Back in 2000, a company called Disappearing Inc. made a presentation to the Bay Area Cypherpunks meeting about their product, which was pretty similar except that back then most people used real email clients instead of webmail. When the guy walked in, and we were expecting him to be pushing some kind of snake oil, he started out by saying that their threat model was to let cooperating people have some guarantee that their email would go away when they wanted it to, not to keep uncooperative people from doing that because you just can't stop screenshots / cameras / sender saving a copy / etc. and anybody trying to sell you that is selling snake oil. And suddenly he had a friendly audience, instead of one that was going to beat him up, because he'd defined a problem that could be believably solved, which was cool.
So the trick is that the file's in an encrypted format, and Disappearing Inc's server keeps the keys and a delete date for them, and if the sender and recipient are both using their product, the reader program/plugin/etc. fetches the key from DI's server; if not, you drop the file into an SSL-encrypted web form on DI which decrypts it for you. When the delete date hits (or earlier, if the file's set for read-only-once), DI deletes their copy of the key, so the recipient's mail box now has an encrypted binary blob file with no decryption key. Yes, if the server gets compromised, it's all toast. Yes, if the recipient's email client or browser is compromised at the time they read it, it's all toast. But if nobody's trying to subpoena or crack the message until after the key's deleted, then it's too late to recover old messages, though you can always try to attack new ones.
It was a nice system, and they stayed in business a couple of years before getting bought by somebody who got bought by somebody and disappearing into dead-dot-com-space. Similar systems have been sold by various other companies, often under category names like "Data Loss Protection".
If you wanted to do a "no forwarding" version, you'd do it by setting rules on who could access it, whether by IP address or some ID in the reader plugin or delete-after-one-read or whatever.