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--- RE: Feature Request: Outgoing Fax (http://www1.pbxes.com/forum/threadid.php?threadid=1266864897)

Feature Request: Outgoing Fax

I hope I can send outgoing fax through Pbxes

RE: Feature Request: Outgoing Fax

Fax and voip is something that has never been ideal.

T38 is a specific fax over voip protocol that truely allows you to sent faxes through ip. T38 is however not widely supported.

That said. I get some faxes once in a while thru normal voip. 80-90 works but some just don't work. The same applies when you use the regular voip protocol thru voip. Many will arrive but some will just not. Reason can be many, old fax equipment bad line. whatever.

PBXes itself has not influence on this. This all comes down to your voip provider and if the support T38 protocol. As far as I know pbxes does not support t38 but when you want to fax you might aswell setup a dedicated dive for sending faxes thru t38 voip outside of pbxes.

The same applies to incoming voip numbers. Very little support t38 protocol.

So fax thru voip in the current situation will never be 100% perfect. I works in most case and that seems to be enough.

RE: Feature Request: Outgoing Fax

In addition to the pertinent information provided by bobmats' post, it should be noted that Fax over IP (FoIP) is having a unique set of issues of its' own.

• First and foremost, T.38 is not a standard. It has not been ratified as a standard in the way SIP or ISDN is, and it might never become one. As a result, there in no really strong incentive for equipment manufacturers to proceed with interoperability tests, to ensure their compliance with a non existent standard.

• For Fax over IP to work properly, every part of the fax call has to support T.38. If it doesn't, the fax transmission might fail. Although fax transmission is so commonplace in our days, its' protocol is based on a very strict set of timers intended for PSTN networks, which tend to expire often in jittery IP networks. The T.38 method has tried and somewhat succeeded to mitigate these factors, but unfortunately is not universally used.

As a result, if the trunk from your ITSP claims to support T.38, take their claim with a grain of salt. Can they guaranty that everyone of their upstream call termination providers support T.38 for FoIP too? Hardly.

A similar fate applies to DIDs. Most of the time their ITSPs don't guaranty T.38 support. So Fax over IP becomes a trial and error proposition. Try and see. No guaranties whatsoever.

However if Fax over IP is important for your operation, you should look into the dedicated services which are specializing in FoIP. They might be able to provide you with some guaranties for fax delivery, albeight at a higher price from a comparable VoIP call.