SMTP server implementations MAY include identification of their
software and version information in the connection greeting reply
after the 220 code, a practice that permits more efficient isolation
and repair of any problems. Implementations MAY make provision for
SMTP servers to disable the software and version announcement where
it causes security concerns.
Considering the amount of troubleshooting that seems to be necessary in resolving some users’ issues, I think that “more efficient isolation and repair of any problems” should be the norm.