It doesn’t have to be reproduce with real data.

Then the developers can do it

So you expect the developer to create data ex-nihilo for a bug they don't know how to trigger ?

I explicitly do not, which is why my first response spells out that it’s hard to reproduce a bug when all your data is gone. If it is the case that the bug can be reproduced without user data (as suggested by the person I responded to, not me), then the developers should be able to do that better than users can.

You can take snapshots of the VM with the mail server. When the bug happens, identify the snapshot. Bingo.

You’re assuming users affected by this bug have control over the VM running their mail server. I won’t argue that it can’t be done, but it’s probably harder than we think.