I need to use plain text authentication. I have to migrate an old
postfix server that uses this authentication mode. I have a lot of
devices configured in this way. I have to plan the migration to TLS,
while I want to use OpenSMTPD with plain text authentication. It's possible?
It's not possible to use plain text authentication with OpenSMTPD.
I guess your migration plan has to give OpenSMTPD a different hostname
or port and let postfix run till ever device is moved to a TLS config.