Perhaps a silly question…
Tomorrow I will be out of office, I need calls to my extension to be forwarded unconditionally to my Voicemail : “I’m not at office, leave a message”
How to do it ?? 
What about if my extension is part of a “ringall” ring group , let’s say just the “customer support” group ??
Do the calls go into my voicemail ?
Thank you
An easy way to forward all of your calls to voice mail is to use the *90*[ext]. This will call forward every call that rings on your phone to your voicemail box.
The problem, as you suspect, is that if your phone rings, it will immediately forward the call to your voice mail.
If you were using queues instead of ring groups, you could have excluded yourself by not logging into the queue, but I don’t think you can get there from here.
Simply put your phone on do not disturb, callers will then be taken to your voicemail. Your phone won’t ring in the ring group either.