Bounces record unhelpful reason in some cases #56
Description
When all remote MXes reject the transaction with 5XX (e.g. due to a missing PTR record), the bounce reason is recorded as "Failure to reach any MX".
The primary point of attack would probably be https://github.com/cmail-mta/cmail/blob/master/cmail-dispatchd/smtp.c#L218
This should be changed to record the SMTP response if one was present.