Gmail Becomes First Major Email Provider To Support MTA-STS and TLS Reporting (zdnet.com)
Google announced this week that Gmail has become the first major email provider to support two new security standards, namely MTA-STS and TLS Reporting. From a report: Both are extensions to the Simple Mail Transfer Protocol (SMTP), the protocol through which all emails are sent today. The purpose of MTA-STS and TLS Reporting is to help email providers establish cryptographically secure connections between each other, with the main goal of twarthing SMTP man-in-the-middle attacks. SMTP man-in-the-middle attacks are a major problem for today's email landscape, where rogue email server operators can intercept, read, and modify the contents of people's emails. The two new standards will prevent this by allowing legitimate email providers to create a secure channel for exchanging emails.
Such as cornering the market for harvesting e-mail content to sell us more targeted ads.
Yes, server to server. My postfix server has been attempting to StartTLS on every outgoing port 25 connection to other mail servers. Many servers (but not all) will speak TLS on port 25.
MTA-STS is analogous to HSTS (HTTP Strict Transport Security). It's a way for MTAs to express that a connection _must_ be encrypted, so if your server connects and attempts a StartTLS that fails, you can distinguish between "doesn't support TLS" and "something fishy is going on." In the latter case the server can avoid sending mail through a possibly-compromised connection.
TLS Reporting is an extension whereby MTA operators can get reports from other MTAs on which mails succeeded or failed. That is, it lets you see how many mails weren't sent due to MTA-STS failures, which could give you an indication that someone is attempting to attack your users.
Schlock Mercenary
Why would I want to secure only segments of the information transfer when this means there are still plenty of points where adversaries can tamper with my email? The better solution has been around for decades already, it's called end-to-end encryption, and implemented for example by GPG.