Many suggestions on transfering emails securely can be found in this answer. But many of them (e.g. PGP) need support from recipient. I want to provide SMTP email server that will route emails of it's clients in the most secure way.
By security I mean:
- Presense of proof that is me who send this message
- No one man in the middle is able to read contents of message
- Preventing other email servers to send message with FROM address containing my domain name (I prefer those emails to be in Junk folder. I'm not sure it's possible)
What are the best ways that will give security without specific support from recipient? (i.e. recipient of email won't have to install plugin/specific program to read email. I know that SMTP itself doesn't offer security. Are there widespread extensions or something like that offer additional security?)
The only known to me way that increases security without recipient support is STARTTLS (it will give me 2 from the above list). But STARTTLS needs support from both ends. Very few major email providers support it nowadays (GMail supports). Does STARTTLS give the same level of protections as TLS in HTTP?
There are many known attacks against TLS in HTTP, e.g. BEAST. Do the same attacks apply to TLS (STARTTLS) as it is used in SMTP? What cipher suites are safe to use with STARTTLS?