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From POP3 To IMAP-What Solutions Are There?
Rhyder asks: "Users were once-happy with a POP3 client and their single desktop or laptop. As the productive portion of the user-base (20% do 80% of the work) moves up in knowledge, implementation and expectations, they simply realize that there should exist something better than a POP3 client. The upper 10% further realize that there must exist an open standard, something beyond Lotus Notes and MS Exchange. Should I implement a GNU server or a commercial server? I refrain from mentioning any packages here, as I do not want to bias a selection. But really, what is the best approach for an IMAP4 server with the posibility of adding on Radius Authentication, Web-based e-mail, possibly a directory service as well? Should a Sendmail core be implemented, or at least used as an MTA? Oh yeah, which OS - Solaris, Linux, BSD, or something else?"
Which software do you recommend?
I'm dealing with a similar situation; I've been looking for open source solutions for a while, and so far, nothing has emerged that's integrated enough to consider.
Requirements (and possible point solutions)
- News server (inn)
- SMTP mail backbone (sendmail)
- POP3 and IMAP4 mail servers (qpopper, cyrus, UW)
- MS-like "shared folders" (Samba)
- group calendaring/scheduling w/Palm conduit (?)
- forms management and workflow (?)
(think purchase requests, expense reporting)
- shared addressbook (something IMAP based?)
- assignable to-do or tasks (?)
- Web client access to all of this
- virus scanning (procmail?)
- Integration among them (e.g. calendar/meeting
requests show up in email, click reply,
calendar entry shows up in your calendar)
- and of course, some way to manage it all.
MS Exchange, Lotus Notes, and HP OpenSomething (OpenMail?) are all candidates in the commercial world.
In the open source world, I think it would currently be a lot of work to put something like this together from the various pieces.
Help me be wrong!
IMAP's great. Server-side folders are key to any real email solution. Thing is, this makes an IMAP server (like a Notes server or an Exchamge server) more CPU- and disk- intensive. You can't support nearly as many people on the same hardware as you can with POP3.
Should you go with IMAP instead of a proprietary commercial maessaging system? Depends. If all you want is e-mail and adddressbooks, an IMAP server and an LDAP server will work just fine, and there are plenty of free web clients for remote access that you can chuck on top of any HTTP server.
But unless you're in an all *nix environment that can use iCal or the KDE or GNOME PIMs, if you plan to do group calendaring, scheduling, shared task lists and so forth, you're better off biting the bullet and going with something commercial, in which case I'd side with Domino/Notes mostly because they have a native Mac client for the non-email functionality, and a web inetrface that even extends to your custom apps, so you're not stuck with putting everyone who needs the scheduling but not on Win32 on feature-restricted webmail (contrast: Exchange). Also, you have a wide range of OSes you can run the server on (from Netware and WnNT to Linux, Solaris and OS/400). The Sun/Netscape/iPlanet suite is a political compromise, since the mail server is pure IMAP.. but as a groupware platform, it ain't no Notes.
Kick those IMAP zealots in the teeth unless they understand they're not going to be able to do any PIM-based, Palm-syncable group calendaring in a heterogeneous environment with Free Software. There are solutions, but no integrated or cross-platform ones. (Insert big asterisk for StarOffice, but that's another story).
That said, my experince has been that of the two free IMAP servers out there, Cyrus outperforms UW-IMAP. The latter puts each "mail folder" in a single mbox-style file, which is nice for POP-IMAP-Pine interoperability, but it also means crummy performance on large mailboxes, since an IMAP server has to "grep" for a full set of message headers every time a folder is accessed. Cyrus seems to do things more efficiently.
What OS do you want to run it on? Unless you're going to be supporting several thousand users or more, use anything you're comfortable with. Linux is plenty fine. BSD is fine. [Insert Un*x flavor here] is fine. If you've got a mainframe that can run it, that's fine too. NT would probably be okay, too, if you don't mind rebooting your mail server once a week or so to prevent memory leaks. If you're doing this for a large university or a large company with 10,000 or more users, the OS matters a bit more if you want to go with a few large servers rather than segmenting your mailboxes onto a bunch of smaller ones. Ah, politics.
Much more important than OS is the way you organize your disks and that you have enough RAM for the job. Assume 2-4MB of RAM will be in use for each user connected to the IMAP server, and since IMAP stays connected until told otherwise, that could mean quite a few people connected all day. As for disks, the faster the better, and if you have a separate drive (or striped drives) for the mail, all the better.
If you're in a mixed-OS environment, I'd go with a PAM-compliant Unix or with Linux. Both Cyrus and UW-IMAP can authenticate against pretty much anything, thanks to the wonder that is PAM. NIS? Fine. An NT domain via pam_smb? Fine. LDAP? Novell? Radius? Ditto.
I'm in the process of implementing CMU's Cyrus IMAP solution. Partner it with a PAM enabled backend, and something like IMP and you've got a webmail interface that does have LDAP abilities for shared address books.
Cyrus also has support for shared IMAP folders, NNTP->IMAP gateways, server-side filtering through sieve.. very cool stuff.
So I'll go ahead and do it...
I use Courier IMAP and Qmail. Qmail provides the POP3 support (for migration), and Courier IMAP does all the external authentication bits you'd need, including IMAP over SSL. I've found Courier IMAP to be extremely stable and fast and works well with my setup (heterogenious environment with pine, Outlook and NS Communicator clients). Currently imapd + couriertcpd are using just over a Meg of RAM.
However, as others have mentioned, it sounds like you're also looking for groupware features. In that case you may be interested in the non-free HP OpenMail, which provides MS exchange server emulation, for things like shared folders, Calendaring and all the other Outlook things.
This is something I think the free software community should be working on - Exchange server interoperability. I hear the Gnome project is working on it with their PIM, but it doesn't sound to me like they're attacking the right angle.
Matt. Want XML + Apache + Stylesheets? Get AxKit.
Yes, there is a solution. It's called fetchmail, and I was amazed at how easy it was to get it set up properly.
pooptruck