Email has been broken on my WordPress install for quite some time. I finally fixed it recently and I wanted a way to monitor usage.

WordPress normally sends transactional emails about things like password resets. The volume is not much on most sites, but it’s important that they’re delivered.

You can pass your Postfix logs through pflogsumm to analyze the logs and make sure everything is healthy and, importantly, that you’re not generating spam emails.

It turns out a website I host for a family member had a contact form that was generating a lot of spam! I switched it to a Jetpack Form with spam protection by Akismet. Problem solved.