https://wiki.asterisk.org/wiki/display/AST/Collecting+Debug+Information

At the Asterisk console:

asterisk -r
logger add channel debug_log_123456 notice,warning,error,debug,verbose,dtmf
core set verbose 3
core set debug 3

Specify the source or destination IP address you want to capture:

sip set debug ip X.X.X.X

Place your call, then disable debugging:

sip set debug off
core set debug off

You may be able to send the log via e-mail like this:

mail -s Log you@yourdomain.tld < /var/log/asterisk/debug_log_123456