I want to send an email that looks like:

Sender: user@A.com
From: xyz@B.com
Reply-To: aaa@C.com
Return-Path: aaa@C.com

A.com is owned by me, and B.com and C.com are owned by a client. I am mostly concerned that email clients will flag this email as spam since the reply-to and return-path are from another domain than the sender. Is this a valid fear?


I haven't seen any that would hold it against you. A quick check of a few spam scanners indicates that if it's even noticed, it must not be a large factor in their spaminess decision.

If you have all your other ducks in a row (SPF or SenderID, DKIM, and DNS) the rest of the message body/headers have significantly less impact on the spaminess score of the message.


I have experienced that setting the Reply-To header does degrade deliverability, in two ways:

  • MailChannels (a SMTP sending service that we use) will funnel messages with a Reply-To through their "junk pool" of IP addresses, almost all of which are on some blacklist (usually at least UCEPROTECT1).
  • SpamAssassin's FREEMAIL_REPLYTO* rules trigger if Reply-To contains a freemail address (gmail, yahoo, hotmail, et al) which doesn't match the From header (which is often true in this use case, since the From header can't be set arbitrarily because of SPF.

If these guys are suspicious of Reply-To, perhaps others are too?

Since we depend on these systems, and want good deliverability, we must use these from headers:

Envelope-From: no-reply@website.com
From: no-reply@website.com

(Where the domain website.com has SPF configured to allow mail sent from the web server and/or SMTP gateway IP addresses. no-reply is used because the "sender" is Website Visitor, and there is no valid address we can use here – it would be silly to allow replies to go to info@website.com.)

This is unfortunate, because the convenience of being able to use email for CRM and easily Reply to the person behind the email is gone. I can't think of a better solution. I have solicited MailChannels to change their policy for sending Reply-Toemails through junk IP addresses, to no effect.

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