Mattias,
these settings have to be configured on the Cisco gateway that is actually doing the T.37.
Here is some example config:
mta send server 10.10.10.1 port 25
mta send subject Fax has been received !!!
mta send postmaster fax-admin@test.com
mta send mail-from hostname cisco-gw.test.com
mta send mail-from username $s$
mta receive aliases test.org
mta receive aliases test.net
mta receive maximum-recipients 20