We have an application sending mail with reply-to addresses in the form of NNN@email.example.com. The mail is sent via Sendgrid and replies are parsed using Sendgrid's Parse API. The problem is some email doesn't get back to us because the reply-to address has been changed to NNN@sendgrid.net. Sendgrid support says they never touch the reply-to and we've confirmed by a Gmail logging account that our application sends mail out correctly. So that leaves me suspecting certain mail servers are switching the domain name with that of the MX host. Our MX records for email.example.com are:
mx3.sendgrid.net 20
mx4.sendgrid.net 20
mx5.sendgrid.net 20
mx.sendgrid.net 10
mx2.sendgrid.net 20
Are there any mail servers or clients that are known to modify reply-to addresses? Or is there any other possible explanation?
Edit Headers from an email send by our app and logged with a Gmail account (sanitized to remove client information):
Delivered-To: [email protected]
Received: by 10.112.62.41 with SMTP id v9csp143404lbr;
Tue, 31 Jul 2012 04:25:29 -0700 (PDT)
Received: by 10.182.51.37 with SMTP id h5mr22717342obo.35.1343733928944;
Tue, 31 Jul 2012 04:25:28 -0700 (PDT)
Return-Path: <[email protected]>
Received: from o1.email.domain.com (o1.email.domain.com. [208.117.48.105])
by mx.google.com with SMTP id m6si10752851oec.6.2012.07.31.04.25.27;
Tue, 31 Jul 2012 04:25:28 -0700 (PDT)
Received-SPF: pass (google.com: domain of [email protected] designates 208.117.48.105 as permitted sender) client-ip=208.117.48.105;
Authentication-Results: mx.google.com; spf=pass (google.com: domain of [email protected] designates 208.117.48.105 as permitted sender) [email protected]; dkim=pass [email protected]
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=Domain.com; h=date
:from:reply-to:to:message-id:subject:mime-version:content-type
:content-transfer-encoding; s=smtpapi; bh=+VZlU9LWGUpMR4neAk/JMo
1DD2E=; b=T3Be3k1Gp+shIGgQZPJ1vtx1kUCRMCRAqRgf8LxVUdvQ1/7YWRKnls
+zrXi6dhJXaLrEyVmt7MyYgxvkVvnJqWYy4tAQABtANQHdLSle4AK1+BY+/m2h4E
fj91rMgQySNbrVV+mhaiE5Q7NxvIa35azUUO0/zRYpluDUt6UBEcQ=
Received: by 10.16.69.117 with SMTP id mf20.27729.5017C0A66
Tue, 31 Jul 2012 06:25:26 -0500 (CDT)
Received: from email.domain.com (unknown [10.60.208.17])
by mi15 (SG) with ESMTP id 5017c0a6.202a.a5e396
Tue, 31 Jul 2012 06:25:26 -0500 (CST)
Date: Tue, 31 Jul 2012 07:25:25 -0400
From: Editors <[email protected]>
Reply-To: [email protected],
Editors <[email protected]>
To: [email protected]
Message-ID: <[email protected]>
Subject: Invitation
Mime-Version: 1.0
Content-Type: text/html;
charset=UTF-8
Content-Transfer-Encoding: 7bit
X-Sendgrid-EID: lcSu+eeYyj7byVT4rUR8IwFlWv7xwmQ9mjigbpHftFWQeg+HlxpNd7F1nbL2uoqLRAg4sHwj57Rrx78FZhDo2L2DCVfamQm0+wEFzkMnensGOv19JFRIAeDMZY53SVpKMwm4Klqcm6L6s9+UaFtqnRUE3/jexZ6uJAFc5x57JG4=
So you see the reply-to is set properly in these headers, but when the recipient replied we saw the reply-to address change to [email protected].
We have the exact same issue. I'm no Exhange guru so I can't validate this - but I'm willing to bet the company you are sending mail to has a configuration flag that states to NOT use a 'reply to' command. Our application sends out as [email protected] with the reply to address set to [email protected]. I can test with gmail and yahoo and it works great!
But certain companies we email always come back t the '[email protected]' address as if there was no reply to set. Think about all the junk mail you get where the reply address is your own email address. I can only imagine MS and Novell have flags to force replies to the actual sender.
Now if we could just get clarification from a real expert as to whether or not this flag is out there.