[MM3-users] How to debug bounces?

Colleagues --

I run a small mailman3 server with perhaps 10 lists. All the lists are small.

Over the past two days about a third of the users in my most active list have been disabled by bounces. I assume the problem is with my setup, not with all of those users.

How do I debug this? Can I see the text of any of the bounce messages to understand why the emails bounced?

This issue might stem from my running somewhat old software. Currently running mailman 3.3.5.

Thanks!

-- Stephen Daniel