We support all of the above - including only authenticated submit port use.
I don't really understand the religious discussion of which protocols
should be supported and which should not be. Support them all and let your
customers decide which ones work for them based on their particular
circumstances at the time and the network they happen to be using.
> Of course, if you're going to do this, you should also be doing
> at least SMTPAUTH and preferably TLSSMTP, but then again many clients
> are broken and don't support these technologies or don't support them
Or you support POP AUTH, which just works, is in widespread use (probably
the most widespread of the methods of authenticating the submit port after
allowing relaying by IP), and was implemented years ago when open relays