I have an odd problem. I tried searching, but honestly, I don't really know what specifically is going on so it's difficult to tack it down.

Basically, whenever someone on our domain sends an email to someone on the same domain, or another domain on the same server, the email on the recipient's side contains headers and all sorts of other garbage. I found this when I tried to create a share with a co-worker. He got an email that included headers and HTML code, but obviously that's not the goal. More critical, is because the HTML isn't being interpreted (that's really just a guess) there were no accept or decline buttons. And, you can't see this in the examples I give below, but I can see it on my screen, the reply-to address is not correct at all. The sender's address is msmith@domaina.com, but the reply-to comes across as Matt@zimbra.domainb.com, again, critical problem.

This is the task share I tried to send to my co-worker (the e-mail he received that should present him with a uniformed share notification with an accept button):
Code:
?= <msmith@domaina.com>
To: gjohnson@domaina.com
Subject: Share Created: Greg shared by Matt =?utf-8?Q?Smith
?=
Message-ID: <c18aa4b0-3415-4931-8fbd-d126845428a2@zimbra-1>
Content-Type: multipart/alternative;
 boundary="=_a7de81fb-09d3-4c91-8d78-04673c16310f"
MIME-Version: 1.0
X-Originating-IP: [192.168.168.170]
X-Mailer: Zimbra 7.1.1_GA_3196 (ZimbraWebClient - FF3.0 (Win)/7.1.1_GA_3196)

--=_a7de81fb-09d3-4c91-8d78-04673c16310f
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit

The following share has been created:

Shared item: Greg (Task Folder)
Owner: Matt Smith


Grantee: gjohnson@domaina.com
Role: Viewer
Allowed actions: View

*~*~*~*~*~*~*~*~*~*
More information in a follow up email
--=_a7de81fb-09d3-4c91-8d78-04673c16310f
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: 7bit

<h3>The following share has been created:</h3>
<p>
<table border="0">
<tr><th align="left">Shared item:</th><td>Greg (Task Folder)</td></tr>
<tr><th align="left">Owner:</th><td>Matt Smith
</td></tr>
</table>
</p>
<table border="0">
<tr><th align="left">Grantee:</th><td>gjohnson@domaina.com</td></tr>
<tr><th align="left">Role:</th><td>Viewer</td></tr>
<tr><th align="left">Allowed actions:</th><td>View</td>
</tr>
</table><p>
<table border="0">
<tr valign="top"><th align="left">Notes:</th><td>More information in a follow up email</td></tr>
</table>
--=_a7de81fb-09d3-4c91-8d78-04673c16310f
Content-Type: xml/x-zimbra-share; charset=utf-8
Content-Transfer-Encoding: 7bit

<share xmlns="urn:zimbraShare" version="0.1" action="new" >
  <grantee id="e2911f83-317a-4ad3-aa87-b3c10b64919f" email="gjohnson@domaina.com" name="gjohnson@domaina.com" />
  <grantor id="8817ed6d-1e83-45db-ba14-dcaf95de9c3c" email="msmith@domaina.com" name="Matt Smith
" />
  <link id="4479" name="Greg" view="task" perm="r" />
  <notes>More information in a follow up email</notes>
</share>
--=_a7de81fb-09d3-4c91-8d78-04673c16310f--
Here is an example of a test e-mail I sent from one domain on our server to another domain on our server, I did this to show that it's an 'any internal to any internal' problem (also having a reply-to address of Matt@zimbra.domainb.com):
Code:
?= <msmith@domaina.com>
To: msmith@domainb.com
Subject: Test
Message-ID: <1978bb3d-a9aa-488e-812c-1347a0eb1077@zimbra-1>
Content-Type: multipart/alternative;
 boundary="=_f9512e63-83cc-4c15-9f5e-375e5a9f39ee"
MIME-Version: 1.0
X-Originating-IP: [192.168.168.170]
X-Mailer: Zimbra 7.1.1_GA_3196 (ZimbraWebClient - FF3.0 (Win)/7.1.1_GA_3196)

--=_f9512e63-83cc-4c15-9f5e-375e5a9f39ee
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit

This is a test, do not reply, do not delete

--=_f9512e63-83cc-4c15-9f5e-375e5a9f39ee
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: 7bit

<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Times New Roman; font-size: 12pt; color: #000000'>This is a test, do not reply, do not delete<br></div></body></html>
--=_f9512e63-83cc-4c15-9f5e-375e5a9f39ee--

It's worth noting that the problem only happens when email is sent through the web interface. Users sending e-mail via a client such as Outlook do not have this issue.

It's also worth noting that this a Zimbra cluster set up with split-DNS. I'm betting it has to do with the DNS because I've had big problems with this in the past, but I really don't know how to solve this one.

I will be glad to share whatever information is necessary, I just don't know what else anyone might need.