Hi all,

We have an issue with a new Exchange 2013 environment consisting of 2 CAS and 2 MBX servers running on Windows 2012 R2. The messages sent from these servers are being bounced by more than 1 enterprise sized organizations using Edge servers without probable cause.. The only error it is giving back is: Remote Server returned '550 5.7.1 Message rejected due to content restrictions'

What was checked/changed sofar:

- Updated Exchange to CU8

- Blacklists

- Reverse DNS addresses

- Sending mail through a 3rd party smarthost

- Enabled header firewall to clean routing info from header

- Told the send connector use HELO instead of EHLO

- Told the send connector to ignore STARTTLS

- Changed RemoteDomain Characterset and NonMimeCharacterSet from ISO-8859-1 to UTF-8

- Changed RemoteDomain LineWrapSize to 78

- Changed RemoteDomain ContentType from MimeHtmlText to MimeText


Now, the following part may be important..

What we now found out is when we forwarded the NDR message to another 3rd party mail server, then forward the NDR from there to the original recipient it will also bounce? Even when we copy a small bit from that NDR or original message into a new email on the working environment the message will get bounced..

I'm getting desperate, please help!! Thanks in advance!


-Emile

• Edited by Emile Dorst Friday, May 08, 2015 8:22 AM