I have a mixed network of analog devices: ATA186's, 8274V's, 1700's with FXS's, and IAD's which interface with the PSTN via AS5300's. What is the best solution for faxing? So far I have worked with Fax passthrough, Modem passthrough, T.38, and cisco fax relay. I've had the best results with the cisco fax relay, but alas it does not work on the ata 186. The ata is limited to modem passthrough and "fax mode". "Fax mode" is not very reliable, particularly with multi page faxes and speeds above 9600 bps. So im looking at modem passthrough, which seems more reliable. My question is: Is modem passthough viable network wide? All of my devices support it, but is modem passthorugh designed for faxing? Any disadvantages?