[exim] Saslauthd and PAM

Hi

I have been reading the thread about pam authentication with interest,
and I have been able to set up saslauthd to use PAM and have it
successfully authenticate using testsaslauthd. However, when trying to
use Exim, it fails. The log file indicates that Exim does not specify a
service name:-

Jan 21 15:58:46 xxx saslauthd[22591]: do_auth         : auth failure: 
[user=testuser] [service=] [realm=] [mech=pam] [reason=PAM auth error]

How does one specify the service name that should be used with saslauthd?

Regards

--
Chris Hills