I have one user that came to me, he had accidentally deleted an email and his recycle bin was empty.
So I checked that and really - a message is deleted, shows up in trash and disappears after about 10 seconds.
My first guess, this is a rule - but no rules are there, except a vacation rule, but its not active and its just a responder.
I checked the client settings for the trash: Tools, Options, Environment, Cleanup:
- Mail and phone: (inactive, set in PO), Manual delete and archive marked
- Appointment, task, and reminder note: Manual delete and archive marked
- Empty trash: Manual marked

Next guess was the mobile phone, so we deleted the GMS account on the (windows) phone - but no change.

I deleted even all proxy access settings, but no change, too.

GWCheck Standalone with "resfldr" - no change.

GW Server/Client is 2014 R2 HP1.

Is there any other option I can check?