An attachment can be taken back

A file a customer emailed you can now be removed, and a record of the removal is kept after the file is gone.

Anyone on your team who can see the conversation can remove a file — you do not need an owner.
A record survives the file — who removed it, when, and what it was called. If you are ever asked whether you held a copy of someone's passport, you can answer.
Deleting is permanent, and the record cannot be edited or removed by anyone, including us.