AdHominem, YOU ARE A GENIUS!
We are getting 100% successful faxes now!!
We're using the same trunks, the same asterisk settings, and the default ATA settings (the Obi 200 you suggested).
So for those of you with fax woes like I was having, and who HAVE to use traditional fax machines, here's our setup:
-Current version of FreePBX as of this post
-Anveo Direct as VSP
-Outbound Service in Anveo setup with a custom route that only uses ATT, Level3, and LANCK, all T.38 enabled routes
*FYI, for inbound (DID), they say all of their US DID's are T.38 capable, even the ones we've ported. So far, that seems to be true
-T.38 Pass through enabled in FreePBX
-Various ISP's at various sites (Verizon, TimeWarner, Telepacific, Cox, Internap)
-All sites tied through ipsec VPN from their SonicWalls to a single HA Cisco ASA setup
-On SonicWalls: all features unchecked on VoIP page
-On ASA, inspect sip removed from config
-ATA: Obi 200. Default settings
-Various fax machines used at various sites. All default settings kept, except send/receive speed set to 9600. Haven't tested faster speeds since the recent successful breakthrough
*Haven't tested non T.38 routes to see if just ulaw works for fax. Just happy the T.38 ones are working!
That's it. Thank you again everyone for your input. I hope this post helps others like me that come across this "white whale" as one put it.