I'm using debian as my webserver and sendmail as my MTA I do NOT have mydomain.com in the hosts file. I have setup sendmail.cf with the following
dnl # Masquerading options
FEATURE(`always_add_domain')dnl
MASQUERADE_AS(`mydomain.com')dnl
FEATURE(`allmasquerade')dnl
FEATURE(`masquerade_envelope')dnl
FEATURE(`masquerade_entire_domain')dnl
MASQUERADE_DOMAIN(`mydomain.com')dnl
However user@mydomain is still being reported as an unknown user by sendmail.
What am I missing?