Environment: Postfix 3.3
In my main.cf file I see references to both smtp and smtpd.
For example:
smtpd security is set here.
smtpd_tls_security_level = may
And just a few lines below smtp security is set in an otherwise identical parameter.
smtp_tls_security_level = may
Other examples are these smtpd parameters:
smtpd_tls_cert_file
smtpd_tls_key_file
Although these aren't exactly the same just a few lines below smtp is used.
smtp_tls_CApath
smtp_tls_CAfile
Question: As far as Postfix is concerned what is the difference between smtp and smtpd?
It's a bit confusing, but generally smtpd handles receiving incoming mail, and smtp handles sending outgoing mail. The confusing naming probably stems from the fact that the SMTP protocol is used by both, the former acts as a server, and the latter as a client.