When does Postfix act as a client? When it sends mail to the outside world?
I'm trying to decide if I should set smtp_tls_session_cache_database
.
There is a similar setting called smtpd_tls_session_cache_database
(smtpd) which is beneficial when Postfix is acting like a server.
smtp_tls_session_cache_database affects the Postfix client TLS session cache and smtpd_tls_session_cache_database affects the Postfix server TLS session cache.
I also read the Postfix TLS readme, but couldn't find what I was looking for.
For what it's worth, my setup has Postfix receiving mail on port 25 (passed to Dovecot) and port 587 setup as SASL auth'd relay (also Dovecot).