Hello, This is on 1.10.6-release-18-1ff9d0a60e~64bit, the latest release version from the repo. I run the following API command to send a TIFF file with txfax: originate {sip_h_P-CustomHeader=value,ignore_early_media=true,fax_ident='Fax Test',origination_caller_id_name='Fax Test',origination_caller_id_number=2165551111,absolute_codec_string=PCMU@20i ,fax_verbose=true,fax_enable_t38=yes,fax_enable_t38_request=yes,fax_use_ecm=no,fax_end_page=1,jitterbuffer_msec=200:200:200}sofia/external/ 4045551111@1.2.3.4:5060 &txfax(/usr/local/etc/faxtiffs/smiley-fine.tif) The INVITE goes out as expected, and the call connects normally. One second later, the far side sends a re-invite for T.38. Local FreeSWITCH shows the remote SDP on the console, sends a 100 Trying, and this appears on the console: [DEBUG] switch_core_media.c:5192 sofia/external/4045551111@1.2.3.4:5060 T38 ACCEPT on request [DEBUG] switch_core_media.c:5296 sofia/external/4045551111@1.2.3.4:5060 T38 IS POSSIBLE on request And then nothing. No 200 OK, 488 Not Acceptable Here, nothing past the 100 Trying. I can't tell why. spandsp.conf.xml is vanilla with only ident, header and spool-dir updated. The environment is relatively simple with all static public IPs, no NAT, etc. This particular FS instance serves only as an endpoint for testing like this fax example. This configuration has been working in general for years and specifically on this box for almost a year. Apparently something has changed somewhere but I can't see what. I'm hoping someone might be able to point me in a direction to diagnose and solve this. Regards, Jeff