Sendmail: subdomain destination problem
I've waded through the Bat Book but haven't come upon anything that will resolve my problem yet. My LAN talks to my ISP's SMTP server (via SMART_HOST). If I send mail to (eg) email@example.com it works fine. If I try to send mail to firstname.lastname@example.org the email is deferred for ever (it retries every 4 hours with the same result - deferred). If I change the address to email@example.com or firstname.lastname@example.org the mail gets sent, but seems to disappear into a black hole (I suspect my ISP's server is doing that) - at least the mail never turns up in the user's mailbox.
What am I missing? I'm using Fedora Core 2 (soon be upgrading to 3) and sendmail v8.12.11.
Any hints, please?