domains as additional labels?

[adixon]

It would be helpful if I can see both the from and to domains when looking at the rejects. It looks like I might be able to do that with a small modification like this:

smtpdRejectsLine = regexp.MustCompile(^NOQUEUE: reject: RCPT from \S+: ([0-9]+) .* from=<.?@(.?)> to=<.?@(.?)>)

I can also see how that might blow up your prometheus for a really big install where you're processing a lot of different from and to domains, but any ideas about the viability of an approach like this?