We just recently began hosting our Web Site and Mail server out of our home. We did a Fresh install of Server 2003 on each server, and set up IIS6 on one and the built in windows mail server on the other. We are having problems with the mail server. POP3 is working fine, we can recieve mail fine. But the SMTP is having problems with sending mail to any domain out side of ours, once we were able to send an email to a yahoo user instantly, now all emails sent show up hours later, the delay times have no consistancy. user1@mydomain.com can send mail to user2@mydomain.com with no problems, they can both recieve and send instantly to each other. they both use the pop3.mydomain.com and smtp.mydomain.com addresses in their outlook. user1 is in Sacramento, and user2 is in Houston. Everything seems to be set up and functioning properly, we have tried many options to get things to work. We Reverted back to using the default 25/110 ports with no luck. on fixing the problem. Why is there such a delay on mails sent to Yahoo/Gmail/Hotmail/etc?

When sending mails to others and get them back, the mails you get back, should normally come from mailer daemon. So in that case, there is an error message in that mail from mailer daemon which tell you, why the mail couldn't be send. Post the error message from the mailer daemon. Please send a reply, if you solved the problem !!!

I'm assuming you meant Exchange when you said windows built-in mailserver? Exchange is by default delivering all mails "itself" so to speak. I.e. it uses DNS to look up the destination and then sends it to the mail server it connects to at that domain. DNS uses ports 53 (both TCP and UDP), and SMTP uses port 25. I'd firstly start off looking at these ports, if they are blocked by a firewall. If not, then make it simple and use a so called 'smart host'. Using a smart host means that instead of your mailserver looking up the destination and sending the mail itself, it simply sends all mails through to another mailserver that has to deal with sending it. The smart host could be any smtp-server you have access to, preferrably your ISP's. Generally just google on different subject like 'configure smart host' if you want to read up on it.

The problem was that Comcast blocks port 25 on residential service. As stated, setting up the smart host to send the mail outside the netowrk worked fine