Okay, so I’ve managed to get the HTML error stripped down a bit. When a
user sends an HTML email from Outlook in I still get this:

Jan 4 18:10:37 src@johnny5 sm-mta[20906]: j050AXJJ020905:
to="|rt-mailgate --queue support --action correspond --url
http://rt.domain.net/", ctladdr=support@rt.domain.net (2/0),
delay=00:00:03, xdelay=00:00:03, mailer=prog, pri=32461, dsn=4.0.0,
stat=Deferred: prog mailer (/usr/sbin/smrsh) exited with EX_TEMPFAIL

Daniel Jimenez