I am currently having an issue receiving FAX to email on our 3CX. We are running v14 SP3 with a Pro license, and are using a 3CX recommened SIP provider. Steps taken: * We have confirmed with the provider that we have T.38 protocol enabled on our SIP trunk * Confirmed that email notifications are being received from the 3CX server, so the mail server is configured correctly. * Our firewall is configured to forward ports 6000-20000 (UDP) to the 3CX server as recommended by our provider, therefore RTP should be included in this range * Temporarily disabled Windows Firewall on the 3CX server to rule this out * Rebooted 3CX server and re-tested * Ensured Fax Service is running I am sending a test fax from a web to fax service, which is failing. When the fax is sent, we get the following logs in the 3CX Activity Log (I've removed info such as FQDN and SIP address for security): 13-Jul-2016 09:57:01.115 [MS105000] C:18.2: No RTP packets were received:remoteAddr=127.0.0.1:10002,extAddr=0.0.0.0:0,localAddr=127.0.0.1:7066 13-Jul-2016 09:57:00.634 Leg L:18.2[Fax] is terminated: Cause: BYE from PBX 13-Jul-2016 09:57:00.634 [CM503008]: Call(C:18): Call is terminated 13-Jul-2016 09:57:00.632 Leg L:18.1[Line:10000<<unavailable] is terminated: Cause: BYE from 126.96.36.199:5060 13-Jul-2016 09:56:34.682 Currently active calls - 1:  13-Jul-2016 09:56:18.121 [CM503007]: Call(C:18): Fax:888 has joined, contact <sip:firstname.lastname@example.org:5006> 13-Jul-2016 09:56:18.121 [CM503007]: Call(C:18): Line:10000<<unavailable has joined, contact <sip:removed:5060> 13-Jul-2016 09:56:18.119 L:18.2[Fax] has joined to L:18.1[Line:10000<<unavailable] 13-Jul-2016 09:56:18.051 [CM503025]: Call(C:18): Calling T:Fax:888@[Dev:sip:email@example.com:5006;user=phone] for L:18.1[Line:10000<<unavailable] 13-Jul-2016 09:56:18.008 [CM503027]: Call(C:18): From: Line:10000<<unavailable ("Fax to Email:" <sip:unavailable@PBX_FQDN:5060>) to T:Fax:888@[Dev:sip:firstname.lastname@example.org:5006;user=phone] 13-Jul-2016 09:56:18.008 [CM503004]: Call(C:18): Route 1: from L:18.1[Line:10000<<unavailable] to T:Fax:888@[Dev:sip:email@example.com:5006;user=phone] 13-Jul-2016 09:56:18.007 [CM505003]: Provider:[ProviderName] Device info: Device Not Identified: User Agent not matched; Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent:  PBX contact: [sip:removed@external_IP:5060] 13-Jul-2016 09:56:18.006 [CM503001]: Call(C:18): Incoming call from Line:10000<<unavailable to <sip:firstname.lastname@example.org:5060> 13-Jul-2016 09:56:18.006 Line limit check: Current # of calls for line Lc:10000(@Provider[<sip:removed:5060>]) is 1; limit is 8 13-Jul-2016 09:56:18.000 [CM503012]: Inbound any hours rule (Fax to Email) for 10000 forwards to Fax:888 I've also run a Wireshark packet capture when sending the fax, and can see that the T.38 protocol is being used (please see Flow Sequence PDF attached). Our SIP provider has suggested that this looks to be a Firewall issue, however we have ruled out Windows Firewall and RTP looks to be forwarded on our main firewall. Can anyone suggest and other things I can check? Thanks in advance!