smtp mail send using "EHLO localhost" in greeting, resulting in Postfix rejection
commento is using /net/smtp SendMail method for sending mail, which results in "EHLO localhost" being used as part of greeting. This is turn results in postfix MTA rejecting mail request:
Jun 27 11:37:27 talk commento: 2019/06/27 11:37:27 [ERROR] smtp_reset_hex.go:23 smtpResetHex(): cannot send reset email: 504 5.5.2 : Helo command rejected: need fully-qualified hostname
Rather the using SendMail create a wrapper function that allows you can have some additional controls on the exchange so you can use fully qualified host name in exchange.
The wrapper will just take the existing /net/smtp function (it is standalone function) add an extra parameter for control options and adjust the behaviour accordingly.
Alternate would be to use different smtp package, but that is likely to require more code changes.
I will test alternate code and post results once done.