Not that this has anything to do with Perl but the Return-path header is not a real SMTP header and you should not include it in your calls to $smtp->datasend().

The Return-path header is added by the final destination MTA and contains the copy value of the actual return path, otherwise known as the envelope from address. In terms of Net::SMTP this is the value that was specified using $smtp->mail($from).

In reply to Re^2: Net::SMTP - To: and From: not appearing in headers? by nobull
in thread Net::SMTP - To: and From: not appearing in headers? by ghenry

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