Hello: I need to know exactly what options need to be specified in sendmail.mc to generate the proper sendmail.cf file so the domain name my ISP sees is valid. Here is some information why this is needed. I have 2 Windows PC and 1 Linux systems and several Home Automation, NAS, Media systems on a home network. I have named running on the Linux system for a local fictional domain called "house.network". I know network is longer than the normal 3 character .com, .net, ..., but it works with no problems as far as name lookup and what have you. I also chose the longer name so there would be no conflict with a real domain name out in the real world and thing on my local network would not get routed to it. I have some of the special systems send email to the Linux system which then has aliases to send certain emails to my ISP email and/or my work email. This is where the problem starts. If the Linux host name is set to system. house.network, then when it connects to the ISP I get error 550 Invalid sender domain. This is because the domain cannot be looked up by the ISP and I can understand why. If I set the Linux host name to system.my_domain.net it works like it should. I registered 2 real domain names (my_domain.com and my_domain.net) with BigDaddy.com partly for this. But when the Linux host name is not in the same domain as the other systems on my local network it cause some other problem. If I add the option in sendmail.mc to generate a sendmail.cf file with Djmy_domain.net and have the Linux host name set to system.house.network the ISP complains with basically the same 550 error. Looking at the returned email some of the header information looks like: Reporting-MTA: dns; my_domain.net Received-From-MTA: DNS; system.house.network Which indicates to me the value of the host name is what my ISP sees that it tries to validate. I have looked at and tried various configurations for masquerading, but have the same problem. It seems to rewrite certain header entries that basically the user's client software look at to display from and to and what have you, but does not change the Received-From-MTA entry. So I hope someone has some good suggestions to help me resolve this problem. ----- Jack Allen -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe https://www.redhat.com/mailman/listinfo/redhat-list