Jeremy Davis's picture

In your config I see:

relayhost = [smtp.office365.com]587

But by my understanding, that should be in the form of [$host]:$port. I.e. should look like this:

relayhost = [smtp.office365.com]:587

Note the missing colon (':')!

Assuming that the relevant password is stored in /etc/postfix/sasl_passwd, then hopefully that might get you over the line?! If not, then perhaps it's worth trying to use the Confconsole plugin. If you try that, I suggest running the "deconfigure" option first.

Please let me know how you get on.