On 17/05/21 9:12 pm, Jaroslaw Rafa wrote:
Dnia 17.05.2021 o godz. 08:52:33 Chris Green pisze:
Most mail clients will use sendmail rather than SMTP on port 25 (or
another port) won't they? As I said my postfix works fine for sending
E-Mails from my MUA (mutt) which uses sendmail.
Most *desktop* mail clients can use either submission or SMTP on port 25
(you can configure that), as they are intended to be used on machines where
no MTA is installed at all, so no sendmail.
This needs to be said because it has been glossed over or missed in this
thread. Email clients use submission or submissions over port 587 or
465 respectively. It is an unfortunately common practice to misuse port
25 for submission and it only (sometimes) works because many mail
servers are configured to allow this incorrect usage due to its
commonality. Port 25 is actually for MX to MX communication and really
isn't supposed to be used for submission at all. So please remember:
Port 465 = submissions = best
Port 587 with mandatory starttls = submission = acceptable
Port 587 with optional starttls or plain text only = not recommended
Port 25 = smtp = not appropriate for submission.
Peter
