Okay, I got this to work using the tool from this site. The download link is dead so I've attached the file at the bottom.
http://blogs.msdn.com/windowsmobile/...hainsaver.aspx
Download and unpack the attached file.
From a command window, run SSLChainSaver.exe (your FQDN) [Enter]
This will pull the certificate information directly from the server (in my case, our Exchange server) and create an xml file in the same folder. A copy of the cert is also saved, but it is not needed.
Change the xml file name to mxip_(whatever you like here).provxml and place it in one of your OEM directories.
The next time you flash your ROM it will be there.
Hurray, my perfect ROM is complete!