I think if you leave a few blank lines at the top of the email it should be ok.
I ran into this when people forwarded email but added no extra lines, so the Command-by-mail extension would intepret “From: email@example.com:firstname.lastname@example.org” at the top of the email body as a command.
Unless someone has better ideas, you could also edit RT-Extension-CommandByMail/lib/RT/Interface/Email/Filter/TakeAction.pm
Somewhere around line 228, add this:
last if $line =~ /^(from:)/i;
(or in your case, replace the “from:” with “ip:”)
Sent: Monday, February 01, 2016 10:56 AM
Subject: [rt-users] bug in rt-mailgate
All email sent to RT is scanned by rt-mailgate for known commands. So far so good, but when a user sends an email with something like that: ip: 10.0.0.0 the rt-mailgate try to interpret ip like a command and return an error email. How can i stop rt to interpret all the strings separated bi “:” from email? Or how can i stop rt to send the error email?