Here's an anonymized pastebin example of my actual log entries of an outgoing email that generated 3 copies: https://pastebin.com/cw2XB5jp to the "catchall" mailbox.
> It is worthwhile to know if the duplicates are caused by adding > multiple 'always_bcc' addresses to the same queue file. > > Look for logging with "message-id=". > > Mar 4 01:05:05 mail postfix/cleanup[30124]: foo: > message-id=<b...@some.mta.name All three emails have the same exact message-id: 004a01d710fe$c29fa920$47defb60$@example.com > Look for "qmgr" logging with "foo", and note the "nrcpt=<number<>" > which indicates the number of recipients. Compare the numbers before > the content filter and after the content filter. It initially is set to 3. Then later it changes to 2.
