Logging improvement ideas: log email subject lines, for successful deliveries log the remote server's response

[cuu508]

I have a couple feature suggestions to do with logging, that I would like to discuss.

To start with, my use case: I want to use maddy logs to investigate outgoing email delivery issues, and diagnose if the issue is on my side, if the remote MTA rejected the message, or if it accepted the message. Typically, when investigating an issue, the things I want to be able to do:

1. Given a specific recipient address, look up the emails maddy has sent to it in a specific time period. Ideally, for each outgoing email I would like to see: date, from address, to address, subject
2. After I've located a specific message, I would like to see all events maddy has logged in relation to it
3. If the message has been rejected by the remote MTA, I also want to see the precise response given by the MTA. This is so that I can tell the recipient – "we tried to deliver the message, here's the response your MTA gave us"
4. If the message has been successfully handed off to a remote MTA, I would also like to see the precise response given by the remote MTA. This is so that I can tell the recipient ""we tried to deliver the message, the remote MTA accepted it with such and such response. If it didn't show up on your end, your MTA ate it."

What I do currently:

Maddy logs to syslog. To look up all emails to [email protected] in the last 12 hours, I do:

journalctl -t maddy --since "12 hours ago" | grep [email protected]

I can look up msg_id for a message I'm interested in, and grep by it to see all related log events

journalctl -t maddy --since "12 hours ago" | grep <msg_id_here>

In case of delivery failure, maddy already logs the response in the smtp_msg and reason fields. In case of successful delivery, maddy logs a "queue: delivered" event, but does not log the exact response given by the remote MTA.

For my use case it would be also helpful to have:

• At some stage of handling the message, log the message's Subject line. It would be convenient to have "from", "to", and "subject" all in one specific log event for easy grepping, but not crucial.
• in case of successful delivery, log the exact response given by the remote MTA