I migrated to Gmail (Google Workspace) and 100k e-mails, all of which seem to be duplicate of legitimate e-mails, say "(unknown sender) (no subject)".
The e-mail body starts by showing e-mail headers in the body of the e-mail. As in, one starts with
16580
Return-Path: xxxx@xxx
How can I get rid of them? Selecting them all and deleting them does not work. Gmail deletes the first 50 of them, promises to get rid of the rest, then nothing happens for days.