Hi,

  According to the release notes of v16.3.670 this was a bug and fixed :

  I would recommend updating to the latest/last v16.3.6989 (Feb 19, 2019)

-dave

Thanks for your reply, David!

Patrick, I would definitely recommend upgrading to the 16.3.6989 release, as it should resolve this issue. Also, please verify that your Bounces Before Removal setting is at the desired threshold. This setting can be found at Domain Settings > General > Mailing Lists card. After the subscriber receives that many bounces, they will be automatically removed from all mailing lists. Along with this setting, you can create a domain event to notify you when a subscriber is removed due to bounces. The event would be created as Mailing List | Mailing List Bounce Removal. Using variables in the Send an Email action, you can list the email address that was removed and the mailing list posting that triggered the removal. 

I will try updating this weekend and see if that helps. I had opened a ticket, I would not expect this to be turned on by default to remove email accounts.

Question on this, if a mailbox was over its limit and could not receive email would that be considered a bounce? And by default they would be removed from the list?

@Patrick, Yea servers should bounce back if the mailbox was full and we'd count that as a bounce. Per the default setting it would get removed after X (based on settings) bounces.