Spam Originating Within Domain
I am currently running a Sendmail Version 8.13.8 mailserver with spamassassin on a Debian 4.1 VM. Recently I have run into issues with spam bots connecting to my SMTP service and sending my users spam messages. They cannot relay out to other domains, but have no trouble sending messages within my domain.
I have tried enabling SMTP authentication but this breaks my receipt of incoming mail.
I am hoping that there is something simple here that I am missing -- have any of you experienced this problem?
Thanks for your time!