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Our webapp sends out mails on behalf of its users. The header fields are set as following:

HEADERFIELD  MAILADDRESS           NAME
------------------------------------------------
from:        [our mail address]    [users name]
reply-to:    [users mail address]  [users name]
sender:      [our mail address]    [name of app]

This is working well, but on a few occasions, when the recipient reply to the mail, the reply is coming back to us (our mail address).

This leads to my question: Does exist mail-clients who does not respect the reply-to field or do we have to look for an explanation elsewhere?

Kara
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Muleskinner
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1 Answers1

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Upsettingly but unsurprisingly, Microsoft Outlook seems to completely ignore Reply-To:

So no, you cannot trust clients (or, you cannot trust Microsoft; story of our lives).

A common arrangement is to use a separate envelope sender (which would display on the client's side as Return-Path: but this is not a header you can meaningfully set from the sender's side as the client's MTA will overwrite it) and simply use From: to set the address where you want the replies. You can also use Sender: to put in a "this is where this message is really from", although Outlook and I believe Gmail will display it as something slightly annoying like "From Name of App on behalf of Users Name".

tripleee
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  • I just tested it, and Reply-To is working for me in Microsoft Outlook 2010. If you hit Reply or Reply All to a message with a Reply-To e-mail address, the reply will be directed to the Reply-To e-mail address, not the From address. Perhaps the above answer by @tripleee is out of date. – RedDragonWebDesign Nov 08 '17 at 11:49
  • I tested this on an Outlook which was available to me at the time, probably O2010 on Exchange 2010 back then. "Unfortunately" I no longer have access to Outlook. Even if there are now versions of Outlook which are not broken in this regard, the answer to the question "are there clients which ignore Reply-To:" is going to remain "Yes", and it's probably not *just* some versions of Outlook. – tripleee Nov 08 '17 at 13:09
  • Yeah. I imagine the explosion of simple mail apps on phones probably hasn't helped the situation any. Not to mention e-mail in general lacks good standards like browsers have (the Acid tests and such). – RedDragonWebDesign Nov 08 '17 at 13:48