Asterisk

This version supports both T.38 passthrough and T.38 termination. We have configuration instructions for both chan_sip and chan_pjsip, be sure that you're using the right configuration!

Chan_SIP

T.38 Passthrough Support

To integrate T38Fax.com with Asterisk to connect a fax machine to a T.38 capable ATA. This will allow a fax machine to send and receive calls via T38Fax.com with Asterisk in the middle.

1. Sign up for a free trial here: Free Trial Signup

2. Check astmoddir (/usr/lib/asterisk/modules) for two standard modules: chan_sip.so and res_rtp_asterisk.so.

   If you do not have both modules, you must recompile asterisk:

   # Asterisk-13
   cd /usr/src
   curl -L -o asterisk-13.cur.tar.gz https://hubs.ly/H097_fC0
   tar xvfz asterisk-13.cur.tar.gz
   rm -rf asterisk-13.cur.tar.gz
   cd asterisk-13.*
   
   ./configure --libdir=/usr/lib64
   make menuselect
   
   # Ensure that the following modules are enabled [*]
   # Channel Drivers/chan_sip
   # Resource Modules/res_rtp_asterisk
   
   make && make install

3. Modify your sip.conf file (/etc/asterisk/sip.conf):

   ; sip.conf
   [general]
   directmedia=no
   t38pt_udptl=yes,redundancy
   register=SIP_USERNAME:SIP_PASSWORD@sip.t38fax.com/SIP_USERNAME

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax account credentials.

   [t38fax]
   type=peer
   context=inboundT38Fax
   port=5080
   qualify=yes
   qualifyfreq=30
   defaultexpiry=300
   insecure=port,invite
   host=sip.t38fax.com
   realm=sip.t38fax.com
   secret=SIP_PASSWORD
   defaultuser=SIP_USERNAME

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax account credentials.

   [ATA_SIP_USERNAME]
   type=friend
   context=outboundT38Fax
   qualify=yes
   qualifyfreq=30
   host=dynamic
   defaultexpiry=300
   secret=ATA_SIP_PASSWORD
   defaultuser=ATA_SIP_USERNAME
   callerid="John Doe" <"CALLERID-NUMBER">

   Please Note: Replace SIP_USERNAME, SIP_PASSWORD, ATA_SIP_USERNAME, and ATA_SIP_PASSWORD with your account information. You may need to add nat=yes depending on your network topology.

4. Add the following to your udptl.conf file (/etc/asterisk/udptl.conf):

   ; udptl.conf
   udptlstart=10000
   udptlend=10999
   T38FaxUdpEC=t38UDPRedundancy

5. Modify/Create your extensions.conf file (/etc/asterisk/extensions.conf):

   [default]
   ; This ensures we reply 200 OK to OPTIONS messages.
   exten => s,1,NoOp( got in default/S )
   
   [inboundT38Fax]
   exten => DIDX1,1,Dial(SIP/DIDX1)
   exten => DIDX2,1,Dial(SIP/DIDX2)
   
   [outboundT38Fax]
   exten => _1NXXNXXXXXX!,1,NoOp(caught 11 digits ${EXTEN})
   exten => _1NXXNXXXXXX!,n,Dial(SIP/${EXTEN}@t38fax)

   Please Note: Replace DIDX1 and DIDX2 with your T38Fax DID numbers.

6. Configure your ATA to connect to Asterisk.

   As an example, to configure a Cisco ATA191:

   1. Follow the steps found here: Cisco ATA191-MPP - Cisco ATA 191 Multiplatform
   2. Navigate to "Voice → Line 1".
   3. Enter your Asterisk Server's address/hostname in the "Proxy" field.
   4. Enter the context you created in Step 2 in the "Display Name" and "User ID" fields.
   5. Enter the password for the context you created in Step 3 in the "Password" field.
   6. Click Submit, and the device should reload its configuration.
   7. In the Asterisk CLI (asterisk -r), enter: sip show peer SIP_USERNAME — look for "Status: OK" and "Addr → IP".

T.38 Termination Support

Coming soon!

Chan_PJSIP

T.38 Passthrough Support

To integrate T38Fax with Asterisk to connect a fax machine to a T.38 capable ATA. This will allow a fax machine to send and receive calls via T38Fax.com with Asterisk in the middle.

1. Sign up for a free trial here: Free Trial Signup

2. Check astmoddir for chan_pjsip.so and res_pjsip.so. If missing, download and compile pjproject, then recompile Asterisk.

   Download & Compile pjproject:

   # PJProject
   cd /usr/src
   curl -L -o pjproject-2.4.tar.bz2 http://www.pjsip.org/release/2.4/pjproject-2.4.tar.bz2
   tar -xjvf pjproject-2.4.tar.bz2
   rm -rf pjproject-2.4.tar.bz2
   cd pjproject-2.*
   
   ./configure CFLAGS="-DNDEBUG" --prefix=/usr --libdir=/usr/lib64 --enable-shared
   
   make dep
   make
   make install
   ldconfig
   
   ldconfig -p | grep pj

   Then recompile Asterisk:

   # Asterisk-13
   cd /usr/src
   curl -L -o asterisk-13.cur.tar.gz https://hubs.ly/H097_fC0
   tar xvfz asterisk-13.cur.tar.gz
   rm -rf asterisk-13.cur.tar.gz
   cd asterisk-13.*
   
   ./contrib/scripts/install_prereq install
   ./configure --libdir=/usr/lib64
   make menuselect
   
   # Ensure that the following modules are enabled [*]
   # Channel Drivers/chan_pjsip
   # Resource Modules/res_pjsip
   
   make && make install

3. Modify your pjsip.conf file (/etc/asterisk/pjsip.conf):

   ; === Transports
   [system-udp]
   type=transport
   protocol=udp
   bind=0.0.0.0:5080
   local_net=172.31.25.0/20
   local_net=127.0.0.1/32
   external_media_address=52.70.17.6 ; Public IP
   external_signaling_address=52.70.17.6
   allow_reload=yes
   
   ; === Trunks
   [t38fax]
   type=registration
   transport=SIP_TRANSPORT
   outbound_auth=t38fax
   server_uri=sip:sip.t38fax.com:5080
   client_uri=sip:SIP_USERNAME@sip.t38fax.com:5080
   retry_interval=60
   contact_user=SIP_USERNAME
   
   [t38fax]
   type=auth
   auth_type=userpass
   password=SIP_PASSWORD
   username=SIP_USERNAME
   
   [t38fax]
   type=aor
   contact=sip:SIP_USERNAME@sip.t38fax.com:5080
   
   [t38fax]
   type=endpoint
   context=inboundT38Fax
   disallow=all
   allow=ulaw
   outbound_auth=t38fax
   aors=t38fax
   direct_media=no
   t38_udptl=yes
   t38_udptl_maxdatagram=400
   t38_udptl_ec=redundancy
   t38_udptl_nat=yes
   from_domain=sip.t38fax.com
   
   [t38fax]
   type=identify
   endpoint=t38fax
   match=sip.t38fax.com

   Please Note: Replace SIP_USERNAME, SIP_PASSWORD, and SIP_TRANSPORT with your T38Fax account information.

   ; === Devices
   [ATA_SIP_USERNAME]
   type=endpoint
   transport=SIP_TRANSPORT
   context=outboundT38Fax
   force_rport=yes
   rtp_symmetric=yes
   direct_media=no
   aors=ATA_SIP_USERNAME
   auth=ATA_SIP_USERNAME
   callerid="T38Fax CallerID"
   disallow=all
   allow=ulaw
   t38_udptl=yes
   t38_udptl_ec=redundancy
   t38_udptl_nat=yes
   
   [ATA_SIP_USERNAME]
   type=aor
   max_contacts=2
   remove_existing=yes
   
   [ATA_SIP_USERNAME]
   type=auth
   auth_type=userpass
   username=ATA_SIP_USERNAME
   password=ATA_SIP_PASSWORD

   Please Note: Replace ATA_SIP_USERNAME, ATA_SIP_PASSWORD, and SIP_TRANSPORT with your account information.

4. Modify/Create your extensions.conf file (/etc/asterisk/extensions.conf):

   [default]
   exten => s,1,NoOp( got in default/S )
   
   [inboundT38Fax]
   exten => DIDX1,1,Dial(PJSIP/DIDX1)
   exten => DIDX2,1,Dial(PJSIP/DIDX2)
   
   [outboundT38Fax]
   exten => _1NXXNXXXXXX!,1,Set(CALLERID(all)="T38Fax" )
    same => n,NoOp(caught 11 digits ${EXTEN})
    same => n,Dial(PJSIP/${EXTEN}@t38fax)

   Please Note: Replace DIDX1 and DIDX2 with your T38Fax DID numbers.

5. Add the following to udptl.conf (/etc/asterisk/udptl.conf):

   ; udptl.conf
   [general]
   udptlstart=10000
   udptlend=10999
   T38FaxUdpEC=t38UDPRedundancy

6. Configure your ATA to connect to Asterisk.

   You should now be able to register your ATA to Asterisk and make/receive fax calls using T.38! If you have any trouble, please open a ticket and one of our Support Engineers will assist you.

T.38 Termination Support

Coming Soon!

This version supports both T.38 passthrough and T.38 termination. Configuration is identical to Asterisk 15 above for both Chan_SIP and Chan_PJSIP, with the exception that the ATA example references a Cisco SPA-112 instead of the ATA191.

T.38 Termination Support

Coming soon!

This version supports both T.38 passthrough and T.38 termination. Configuration is identical to Asterisk 15 above for both Chan_SIP and Chan_PJSIP.

T.38 Termination Support

Coming soon!

In Asterisk 12, a new SIP channel driver (chan_pjsip) was introduced.

This version supports both T.38 passthrough and T.38 termination.

T.38 Passthrough Support

1. Sign up for a free trial here: Free Trial Signup

2. Check astmoddir for chan_sip.so and res_rtp_asterisk.so. If missing:

   # Asterisk 11
   cd /usr/local/src
   wget -O asterisk-11.cur.tar.gz https://hubs.ly/H0981kw0
   tar xvfz asterisk-11.cur.tar.gz
   rm -rf asterisk-11.cur.tar.gz
   cd asterisk-11.*
   ./configure
   make menuselect
   # Ensure that the following modules are enabled [*]
   # Channel Drivers/chan_sip
   # Resource Modules/res_rtp_asterisk
   make install

3. Modify your sip.conf file (/etc/asterisk/sip.conf):

   ; sip.conf
   directmedia=no
   t38pt_udptl=yes,redundancy
   register=SIP_USERNAME:SIP_PASSWORD@sip.t38fax.com/SIP_USERNAME

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax account credentials.

   [t38fax]
   type=peer
   context=inboundT38Fax
   qualify=yes
   qualifyfreq=30
   defaultexpiry=300
   insecure=port,invite
   host=sip.t38fax.com
   realm=sip.t38fax.com
   defaultuser=SIP_USERNAME
   secret=SIP_PASSWORD

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax account credentials.

   [SIP_USERNAME]
   type=friend
   context=outboundT38Fax
   qualify=yes
   qualifyfreq=30
   host=dynamic
   defaultexpiry=300
   defaultuser=SIP_USERNAME
   callerid="John Doe"
   secret=YOUR_ATA_PWORD

   Please Note: Replace all placeholder values. You may need to add nat=yes depending on your network topology.

   Add the following to udptl.conf (/etc/asterisk/udptl.conf):

   ; udptl.conf
   udptlstart=10000
   udptlend=10999
   T38FaxUdpEC=t38UDPRedundancy

4. Modify/Create your extensions.conf file (/etc/asterisk/extensions.conf):

   [default]
   exten => s,1,NoOp( got in default/S )
   
   [inboundT38Fax]
   exten => DIDX1,1,Dial(SIP/DIDX1)
   exten => DIDX2,1,Dial(SIP/DIDX2)
   
   [outboundT38Fax]
   exten => _1NXXNXXXXXX!,1,NoOp(caught 11 digits ${EXTEN})
   exten => _1NXXNXXXXXX!,n,Dial(SIP/${EXTEN}@t38fax)

   Please Note: Replace DIDX1 and DIDX2 with your T38Fax DID numbers.
5. Configure your ATA (e.g. Cisco SPA-112):
   1. Follow the steps found here: Cisco SPA-112 Configuration Guide
   2. Navigate to "Voice → Line 1".
   3. Enter your Asterisk Server's address/hostname in the "Proxy" field.
   4. Enter the context in "Display Name" and "User ID" fields.
   5. Enter the password in the "Password" field and click Submit.
   6. In Asterisk CLI: sip show peer SIP_USERNAME

T.38 Termination Support

1. Sign up for a free trial here: Free Trial Signup

2. Prepare your system:

   # CentOS 7.x/6.x
   yum -y install perl cpan libyaml perl-YAML perl-Time-HiRes libwww-perl
   
   # CentOS 7.x
   yum -y install libtiff-tools
   
   # CentOS 6.x
   yum -y install libtiff libtiff-devel

3. Install mime-construct support tools:

   PERL_MM_USE_DEFAULT=1 perl -MCPAN -e "install Proc::WaitStat"
   PERL_MM_USE_DEFAULT=1 perl -MCPAN -e "install MIME::Types"

4. Install mime-construct:

   cd /usr/local/src
   wget http://search.cpan.org/CPAN/authors/id/R/RO/ROSCH/mime-construct-1.11.tar.gz
   tar xvfz mime-construct-1.11.tar.gz
   rm -rf mime-construct-1.11.tar.gz
   cd mime-construct-1.11
   perl Makefile.PL
   make install

5. Install spandsp:

   # Inst. SpanDSP
   cd /usr/local/src
   wget http://www.soft-switch.org/downloads/spandsp/spandsp-0.0.6.tar.gz
   tar xvfz spandsp-0.0.6.tar.gz
   rm -rf spandsp-0.0.6.tar.gz
   cd spandsp-0.0.6
   ./configure --prefix=/usr
   make
   make install

6. Check astmoddir for four modules: chan_sip.so, res_rtp_asterisk.so, res_fax.so, res_fax_spandsp.so. If missing:

   # Asterisk 11
   cd /usr/local/src
   wget -O asterisk-11.cur.tar.gz https://hubs.ly/H0981kw0
   tar xvfz asterisk-11.cur.tar.gz
   rm -rf asterisk-11.cur.tar.gz
   cd asterisk-11.*
   ./configure
   make menuselect
   # ensure the following four modules are enabled [*]
   # Channel Drivers/chan_sip
   # Resource Modules/res_rtp_asterisk
   # Resource Modules/res_fax
   # Resource Modules/res_fax_spandsp
   make install

7. Modify your sip.conf file (/etc/asterisk/sip.conf):

   ; sip.conf
   t38pt_udptl=yes,redundancy
   register=SIP_USERNAME:SIP_PASSWORD@sip.t38fax.com/SIP_USERNAME

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax.com account credentials.

   [t38fax]
   type=peer
   context=inboundT38Fax
   qualify=yes
   qualifyfreq=300
   defaultexpiry=600
   insecure=port,invite
   host=sip.t38fax.com
   realm=sip.t38fax.com
   defaultuser=SIP_USERNAME
   secret=SIP_PASSWORD

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax.com account credentials.

8. Modify/Create your extensions.conf file (/etc/asterisk/extensions.conf):

   [globals]
   VSA=/var/spool/asterisk
   FAXRCPT=YOUR_ADDR@EXAMPLE.COM
   
   [default]
   exten => s,1,NoOp( got in default/S )
   
   [inboundT38Fax]
   exten => s,n,Goto(fax,rx,1)
   
   [fax]
   exten => rx,1,NoOp( ** RECEIVING FAX ** )
   exten => rx,n,Answer
   exten => rx,n,StopPlaytones
   exten => rx,n,Set(FAXFILEBASE=${VSA}/fax/${CALLERID(num)}-${EPOCH})
   exten => rx,n,Set(FAXFILE=${FAXFILEBASE}.tif)
   exten => rx,n,Wait(1)
   exten => rx,n,ReceiveFAX(${FAXFILE})
   
   exten => tx,1,NoOp( ** SENDING FAX ** )
   exten => tx,n,Wait(6)
   exten => tx,n,Set(FAXOPT(localstationid)=SIP_USERNAME)
   exten => tx,n,SendFAX(${VSA}/fax/channel-001.tiff,dfz)
   
   exten => h,1,Noop(FAX ${FAXOPT(status)} from ${CALLERID(all)}: ${FAXOPT(error)})
   exten => h,n,System(/usr/local/script/fax2mail -p --cid-name ${CALLERID(name)} --cid-number ${CALLERID(num)} --dest-exten ${DNID} --dest-email ${FAXRCPT} -f ${FAXFILEBASE})
   exten => h,n,NoOp(FAXOPT(ecm) : ${FAXOPT(ecm)})
   exten => h,n,NoOp(FAXOPT(filename) : ${FAXOPT(filename)})
   exten => h,n,NoOp(FAXOPT(headerinfo) : ${FAXOPT(headerinfo)})
   exten => h,n,NoOp(FAXOPT(localstationid) : ${FAXOPT(localstationid)})
   exten => h,n,NoOp(FAXOPT(maxrate) : ${FAXOPT(maxrate)})
   exten => h,n,NoOp(FAXOPT(minrate) : ${FAXOPT(minrate)})
   exten => h,n,NoOp(FAXOPT(pages) : ${FAXOPT(pages)})
   exten => h,n,NoOp(FAXOPT(rate) : ${FAXOPT(rate)})
   exten => h,n,NoOp(FAXOPT(remotestationid) : ${FAXOPT(remotestationid)})
   exten => h,n,NoOp(FAXOPT(resolution) : ${FAXOPT(resolution)})
   exten => h,n,NoOp(FAXOPT(status) : ${FAXOPT(status)})
   exten => h,n,NoOp(FAXOPT(statusstr) : ${FAXOPT(statusstr)})
   exten => h,n,NoOp(FAXOPT(error) : ${FAXOPT(error)})
   
   exten => _[it],1,Hangup()

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax.com account credentials.

9. Install fax2mail script:

   mkdir -p /usr/local/script
   cd /usr/local/script
   wget -O fax2mail https://bitbucket.org/T38Guru/fax2mail/raw/78ea18ee5b1f9273e4062010750c8e08bd20770a/fax2mail
   chmod ugo+x fax2mail

10. Make the fax directory:

    mkdir /var/spool/asterisk/fax

    Please Note: TIFF files will accumulate in /var/spool/asterisk/fax. Use cron or another method to periodically remove them.

This was the first release that included T.38 Fax Gateway Support.

https://wiki.asterisk.org/wiki/display/AST/T.38+Fax+Gateway

T.38 Passthrough Support

1. Sign up for a free trial here: Free Trial Signup

2. Check astmoddir for chan_sip.so and res_rtp_asterisk.so. If missing:

   # Asterisk 1.8
   cd /usr/src
   wget -O asterisk-1.8.cur.tar.gz https://hubs.ly/H0981pZ0
   tar xvfz asterisk-1.8.cur.tar.gz
   rm -rf asterisk-1.8.cur.tar.gz
   cd asterisk-1.8.*
   ./configure
   make menuselect
   # Ensure that the following two modules are enabled [*]
   # Channel Drivers/chan_sip
   # Resource Modules/res_rtp_asterisk
   make install

3. Modify your sip.conf file (/etc/asterisk/sip.conf):

   ; sip.conf
   directmedia=no
   t38pt_udptl=yes,redundancy
   register=SIP_USERNAME:SIP_PASSWORD@sip.t38fax.com/SIP_USERNAME

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax.com account credentials.

   [t38fax]
   type=peer
   context=inboundT38Fax
   qualify=yes
   defaultexpiry=600
   insecure=port,invite
   host=sip.t38fax.com
   realm=sip.t38fax.com
   defaultuser=SIP_USERNAME
   secret=SIP_PASSWORD

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax.com account credentials.

   [SIP_USERNAME]
   type=friend
   context=outboundT38Fax
   qualify=yes
   qualifyfreq=600
   host=dynamic
   defaultexpiry=600
   defaultuser=SIP_USERNAME
   callerid="John Doe"
   secret=ATA_SIP_PASSWORD

   Please Note: Replace all placeholder values. You may need to add nat=yes depending on your network topology.

   Add the following to udptl.conf (/etc/asterisk/udptl.conf):

   ; udptl.conf
   udptlstart=10000
   udptlend=10999
   T38FaxUdpEC=t38UDPRedundancy

4. Modify/Create your extensions.conf file (/etc/asterisk/extensions.conf):

   [default]
   exten => s,1,NoOp( got in default/S )
   
   [inboundT38Fax]
   exten => DIDX1,1,Dial(SIP/DIDX1)
   exten => DIDX2,1,Dial(SIP/DIDX2)
   
   [outboundT38Fax]
   exten => _1NXXNXXXXXX!,1,NoOp(caught 11 digits ${EXTEN})
   exten => _1NXXNXXXXXX!,n,Dial(SIP/${EXTEN}@t38fax)

   Please Note: Replace DIDX1 and DIDX2 with your T38Fax.com DID numbers.
5. Configure your ATA (e.g. Cisco SPA-112):
   1. Follow the steps found here: Cisco SPA-112 Configuration Guide
   2. Navigate to "Voice → Line 1".
   3. Enter your Asterisk Server's address/hostname in the "Proxy" field.
   4. Enter the context in "Display Name" and "User ID" fields.
   5. Enter the password in the "Password" field and click Submit.
   6. In Asterisk CLI: sip show peer SIP_USERNAME

T.38 Termination Support

1. Sign up for a free trial here: Free Trial Signup

2. Prepare your system:

   # CentOS 7.x/6.x
   yum -y install perl cpan libyaml perl-YAML perl-Time-HiRes libwww-perl
   
   # CentOS 7.x
   yum -y install libtiff-tools
   
   # CentOS 6.x
   yum -y install libtiff

3. Install mime-construct support tools:

   PERL_MM_USE_DEFAULT=1 perl -MCPAN -e "install Proc::WaitStat"
   PERL_MM_USE_DEFAULT=1 perl -MCPAN -e "install MIME::Types"

4. Install mime-construct:

   cd /usr/local/src
   wget http://search.cpan.org/CPAN/authors/id/R/RO/ROSCH/mime-construct-1.11.tar.gz
   tar xvfz mime-construct-1.11.tar.gz
   rm -rf mime-construct-1.11.tar.gz
   cd mime-construct-1.11
   perl Makefile.PL
   make install

5. Install spandsp:

   # SpanDSP
   cd /usr/src
   wget http://www.soft-switch.org/downloads/spandsp/spandsp-0.0.6.tar.gz
   tar xvfz spandsp-0.0.6.tar.gz
   rm -rf spandsp-0.0.6.tar.gz
   cd spandsp-0.0.6
   ./configure --prefix=/usr
   make
   make install

6. Check astmoddir for four modules: chan_sip.so, res_rtp_asterisk.so, res_fax.so, res_fax_spandsp.so. If missing:

   # Asterisk 1.8
   cd /usr/src
   wget -O asterisk-1.8.cur.tar.gz https://hubs.ly/H0981pZ0
   tar xvfz asterisk-1.8.cur.tar.gz
   rm -rf asterisk-1.8.cur.tar.gz
   cd asterisk-1.8.*
   ./configure
   make menuselect
   # Ensure the following four modules are enabled [*]
   # Channel Drivers/chan_sip
   # Resource Modules/res_rtp_asterisk
   # Resource Modules/res_fax
   # Resource Modules/res_fax_spandsp
   make install

7. Modify your sip.conf file (/etc/asterisk/sip.conf):

   ; sip.conf
   t38pt_udptl=yes,redundancy
   register=SIP_USERNAME:SIP_PASSWORD@sip.t38fax.com/SIP_USERNAME

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax.com account credentials.

   [t38fax]
   type=peer
   context=inboundT38Fax
   qualify=yes
   qualifyfreq=30
   insecure=port,invite
   defaultexpiry=300
   host=sip.t38fax.com
   realm=sip.t38fax.com
   defaultuser=SIP_USERNAME
   secret=SIP_PASSWORD

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax.com account credentials.

8. Modify/Create your extensions.conf file (/etc/asterisk/extensions.conf):

   [globals]
   VSA=/var/spool/asterisk
   FAXRCPT=YOUR_EMAIL@EXAMPLE.COM
   
   [default]
   exten => s,1,NoOp( got in default/S )
   
   [inboundT38Fax]
   exten => s,n,Goto(fax,rx,1)
   
   [fax]
   exten => rx,1,NoOp( ** RECEIVING FAX ** )
   exten => rx,n,Answer
   exten => rx,n,StopPlaytones
   exten => rx,n,Set(FAXFILEBASE=${VSA}/fax/${CALLERID(num)}-${EPOCH})
   exten => rx,n,Set(FAXFILE=${FAXFILEBASE}.tif)
   exten => rx,n,Wait(1)
   exten => rx,n,ReceiveFAX(${FAXFILE})
   
   exten => tx,1,NoOp( ** SENDING FAX ** )
   exten => tx,n,Wait(6)
   exten => tx,n,Set(FAXOPT(localstationid)=SIP_USERNAME)
   exten => tx,n,SendFAX(${VSA}/fax/channel-001.tiff,dfz)
   
   exten => h,1,Noop(FAX ${FAXOPT(status)} from ${CALLERID(all)}: ${FAXOPT(error)})
   exten => h,n,System(/usr/local/script/fax2mail -p --cid-name ${CALLERID(name)} --cid-number ${CALLERID(num)} --dest-exten ${DNID} --dest-email ${FAXRCPT} -f ${FAXFILEBASE})
   exten => h,n,NoOp(FAXOPT(ecm) : ${FAXOPT(ecm)})
   exten => h,n,NoOp(FAXOPT(filename) : ${FAXOPT(filename)})
   exten => h,n,NoOp(FAXOPT(headerinfo) : ${FAXOPT(headerinfo)})
   exten => h,n,NoOp(FAXOPT(localstationid) : ${FAXOPT(localstationid)})
   exten => h,n,NoOp(FAXOPT(maxrate) : ${FAXOPT(maxrate)})
   exten => h,n,NoOp(FAXOPT(minrate) : ${FAXOPT(minrate)})
   exten => h,n,NoOp(FAXOPT(pages) : ${FAXOPT(pages)})
   exten => h,n,NoOp(FAXOPT(rate) : ${FAXOPT(rate)})
   exten => h,n,NoOp(FAXOPT(remotestationid) : ${FAXOPT(remotestationid)})
   exten => h,n,NoOp(FAXOPT(resolution) : ${FAXOPT(resolution)})
   exten => h,n,NoOp(FAXOPT(status) : ${FAXOPT(status)})
   exten => h,n,NoOp(FAXOPT(statusstr) : ${FAXOPT(statusstr)})
   exten => h,n,NoOp(FAXOPT(error) : ${FAXOPT(error)})
   
   exten => _[it],1,Hangup()

   Please Note: Replace SIP_USERNAME and SIP_PASSWORD with your T38Fax.com account credentials.

9. Install fax2mail script:

   mkdir -p /usr/local/script
   cd /usr/local/script
   wget -O fax2mail https://bitbucket.org/T38Guru/fax2mail/raw/78ea18ee5b1f9273e4062010750c8e08bd20770a/fax2mail
   chmod ugo+x fax2mail

10. Make the fax directory:

    mkdir /var/spool/asterisk/fax

    Please Note: TIFF files will accumulate in /var/spool/asterisk/fax. Use cron or another method to periodically remove them.

T.38 Passthrough & T.38 Termination (receives faxes via ReceiveFax)

T.38 Passthrough Only. T.38 Passthrough allows Asterisk to carry T.38 UDPTL from one T.38-speaking endpoint to another T.38-speaking endpoint. Asterisk does not modify the media.

No T.38 capability at all.