Hello.
I arrive to this post so late but I'll describe my experience.
My problem was the same that seederp2p, people send me faxes, all ok in the other side but in my Issabel there was no faxes, no emails and nothing new in the fax viewer. My PBX was migrated from Elastix too.
I did all that bustosjuan said and all work now fine. In ask to the question of the time zone, my php.ini had ";date.timezone =" (commented and empty" and I modified it to "date.timezone = Europe/Madrid
" and the time was ok.
I hope it help any one.
Thanks.