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All you need is another port in addition to the regular SMTP port. They are not mutually exclusive.
by drudru11 8y ago
All you need is another port in addition to the regular SMTP port. They are not mutually exclusive.
- mike-cardwell 8y agoThat is completely insecure. A MITM would just block access to the tls-on-connect port, forcing the sending host to retry on port 25, where they would strip the STARTTLS advertisement. Unless you're recommending to not fall back to port 25 after a failed connection to the tls-on-connect port. In which case, see the comment you were replying to where I said it would be backwards incompatible. Both of the solutions I mentioned are backwards compatible, and protected from a similar downgrade situation.
- drudru11 8y agoRight, I should have said that I was recommending not ever sending on 25. The STARTTLS mitm is just too easy for large attackers. IMHO, being backwards compatible is necessary for a transition period. The messaging to SMTP operators should be... get on board, or you are going to start losing mail in 1 year. Even Chrome is going to show all http as insecure in the very near future. Which reminds me... I need to get all my sites upgraded.