Bounce attack validation - what am I missing?

One of my users had to send 1,000 Emails, using mail merge.

Obviously, when you send such a large quantity of Emails at once, some will bounce back, for multiple reasons.

However, this is what I am seeing in SMG Message Audit Logs:

The list goes on, but with similar results - the bounce is either intended for prvs=XXXXXX=csylvie@domain.com and then it is rejected as All recipients are invalid, or it is intended for csylvie@domain.com and then it is rejected for failing bonce attack validation.

Can someone please clarify?