After installing Exchange 2013 Service Pack 1, people reported issues with Transport Agents. Symptoms are that the Transport service doesn’t start or stops shortly after starting the service or you can’t install the 3rd party product.

Products experiencing the issue are TrendMicro ScanMail, McAfee Email Security (GroupShield), Symantec Mail Security for Exchange, AVG for Servers, ESET Mail Security for Exchange and CodeTwo Exchange Rules. Products from other vendors may be affected as well.

Microsoft is aware of this issue and has published KB2938053 which has a small Exchange2013-KB2938053-FixIt.zip script to fix the issue.

The cause of the issue lies in XML files containing invalid XML markup in the form of “comments” which prevents .NET from loading the XML files, e.g.

<!-- 15.0.847.30 -------------------------------->

The two files containing the invalid XML markup are:

$Env:Windir\Microsoft.NET\assembly\GAC_MSIL\policy.8.0.Microsoft.Exchange.Data.Common\v4.0_15.0.847.30__31bf3856ad364e35\Microsoft.Exchange.Data.Common.VersionPolicy.cfg
$Env:Windir\Microsoft.NET\assembly\GAC_MSIL\policy.8.0.Microsoft.Exchange.Data.Transport\v4.0_15.0.847.30__31bf3856ad364e35\Microsoft.Exchange.Data.Transport.VersionPolicy.cfg

Be advised that the script supplied in the KB article tries to locate and fix various alternate versions of those files. Something you might want to consider as well when fixing it manually, should you be unable to locate the specific files mentioned above.

After running the script you should be able to start the Transport service or install 3rd party containing transport agents..

Update (3/5): Updated blog after official KB article got published. The issue was also blogged on by fellows Jason Sherry, Paul Cunningham while Tony Redmond has additionanal background details here.