net/smtp: can not use PlainAuth without call to StartTLS

[gopherbot]

by linuxhacker100:

In the smtp package it is impossible to use plain authentication without calling
StartTLS. This even happens when you manually make the client with a tls.Conn. There are
times when you want to force plain auth even if the client does not know encryption is
in use. There could be a VPN or the underlying connection may be encrypted or local.

[rsc]

Comment 1:

I think the benefits of making sure people don't send passwords in
clear text over networks accidentally outweigh the inconvenience of
not being able to use PlainAuth when you do intend to send a password
over a network in clear text.
PlainAuth is just a helper and does not do anything that requires help
from net/smtp.  I would suggest to copy the PlainAuth implementation
into your own package and delete the lines that require TLS.  It's
under 20 lines of code.

Status changed to WorkingAsIntended.

[gopherbot]

Comment 2 by linuxhacker100:

I ended up just using StartTLS (instead of TLS.Conn). However, it would be nice if there
was a way to override the default.
Yes, copying the code is probably what I would do if StartTLS was not an option.