so, I have my postfix+dovecot setup working fine. I have an issue though
right now, postfix authenticates senders using SASL against Dovecot, which is working nice
however, I want to be able to send emails from addresses without a mailbox associated (for example, for notifications from my accounts). so I don't want to have those accounts registered in dovecot. and it doesn't seem like postfix supports several authentication mechanisms at the same time