This can lead to the sending of email to the correct address but the wrong recipient.
3 Matching Annotations
- Dec 2022
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www.rfc-editor.org www.rfc-editor.org
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- Nov 2022
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stackoverflow.com stackoverflow.com
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You can definitely set the Return-Path header as a sender. But yes, some receivers might rewrite it (But not always ), or depending on who you're sending through, it might be re-written by them. For instance when using MailGun to send bulk email you have to do things just right in order to set a Return-Path that will be preserved. I know this contradicts the RFC you cite, but it's in practice true.
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Return-Path header is written by the receiving server, not by the sending server. And as per the RFC 5321, it is the same as the address supplied in MAIL FROM command.
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