A PHP scri_pt on a Linux (Redhat) web server that I maintain sends email for various types of notifications: new user registrations, replies to forum posts, etc.

Most of these notifications are received, but some are reported as not being received, and I'm trying to figure out why.

I've looked at the sendmail log (/etc/maillog), and can't find any errors. I don't have access to the logs on the receiving side.

Sendmail has a zillion configuration parameters. most of which I don't understand.

Is there a way of getting sendmail to produce a more detailed log, maybe showing the low-level "HELO" type messages?