Detecting Outlook autoreply/out-of-office emails
Look for these headers:
- x-autorespond
- precedence or x-precedence with value "auto_reply", "bulk" or "junk"
- auto-submitted with value "auto-replied"
- x-auto-response-suppress (not always, see answer below)
And subjects starting with:
- Auto:
- Automatic reply
- Autosvar
- Automatisk svar
- Automatisch antwoord
- Abwesenheitsnotiz
- Risposta Non al computer
- Automatisch antwoord
- Auto Response
- Respuesta automática
- Fuori sede
- Out of Office
- Frånvaro
- Réponse automatique
This question often comes up in Google, so I decided to add an important note.
Don't ever use X-Auto-Response-Suppress in your filters as suggested in the other answer.
X-Auto-Response-Suppress is used by Exchange to tell other servers to not send auto-replies in response to an email. It doesn't mean that this email is an auto-response.
We had to learn it the hard way, hope you won't have to. I've also wrote a blog post with more details: http://www.jitbit.com/maxblog/18-detecting-outlook-autoreplyout-of-office-emails-and-x-auto-response-suppress-header/
It's worth noting that Exchange is supposed to suppress out-of-office emails in response to messages with a Precedence:bulk or X-Auto-Response-Suppress:OOF header:
http://blogs.technet.com/b/exchange/archive/2006/10/06/3395024.aspx