Looking at the archives, this has been an on again-off again thing for quite a few years. Yes, this is about having the Subject header line contain a queue name or some such identifier, mostly so it “looks nice”. Alas, the Subject heading does play a big role in appearance and thus the buy-in of this from our user population.
I looked at Branded Queue extension, though I’ve not gotten it to work easily with RT-3.6.3 through 3.6.7. If anyone has done so, I’d greatly appreciate a note.
The general recommendation on the list has been to just run multiple instances of RT. That would work, at the expense of duplicating a lot of material. But it’s probably the easiest. We’re evaluating if that’s worth it, just to get this one feature.
However, the preference is for a single instance of a RT database. We don’t mind if the Ticket Number is incremented even though it’s different queues. So English Department #1, and the next ticket might be Physics Department #2 (rather than the first Physics ticket being #1 as well.) That’s fine by us. Nobody’s really keeping track of actual ticket numbering patterns 
So why a single instance? Same set of support staff. So while we’d like the staff of English department to mail english-support@ and get a reply using “Subject English Department Help Desk #x”, and Physics staff members send to physics-support@ and get a reply with “Subject Physics Department Help Desk #x”, it all goes into the same RT system. The actual support staff behind the scenes are the same.
With multiple instances of RT (which I’m guessing involve a separate RT_SiteConfig.pm with $DatabaseName set differently) the staff would have to login to multiple RTs. We’re bound to forget sooner or later.
I was thinking of changing /opt/rt3/lib/RT/Action/SendEmail.pm SetSubjectToken function to change the outgoing Subject. Then using the built-in $EmailSubjectTagRegex to be (English|Physics) Department Help Desk. I’m still not sure about Callbacks, vs Overlays, vs local directory. Or just being old-school and editing the original file directly (at least I understand how that works.)
I’ve not really though through what happens if a ticket moves from the English queue to the Physics queue, but I think it’d still be ok. The ticket number is still unique. And upon receiving the email, RT would still match against both Physics… and English… in the Subject heading.
Tips, advice, warnings, etc welcome.
Thank you,
PH
Paul Hirose : pthirose@ucdavis.edu : Sysadm Motto: rm -fr /MyLife