I am having trouble trying to figure out how to setup a mail server. Right now I am able to send mail from my server without a problem using send mail. However I have no idea how to set it up to recieve e-mail. I am using a free DNS at no-ip.com and I have setup my MX there as being ruggles.hopto.org which goes back to my server. However if I try e-mailing root@ruggles.hopto.org it doesn't get there. I am also behind a firewall and I am port forwarding ports 110 and 25. Any help on how to recieve e-mail from the outside would be great. Thanks

Anyone please. I don't even know where to begin to find information about this

You said you can send email to the outside ?

if (true) {
How did you that working ?
when I do "command | mail username@hostname.com
I get it returned.
}
thanks();

first check that your dns server points to your server
2.) your sendmail is setup and working
3.) your pop3 server is setup and working

yes that is true. That part was pre-setup by my linux install. I use Pine to send the message through send mail.

1) How do I check if the dns server points to my server. If I ping ruggles.hopto.org it does bring up my internet IP.

2) send mail is up and working just fine.

3) This is the part I need help with. How do I set up the pop3 server? what program is used etc...?

well if you have sendmail running then you will have information ready and waiting for you in /var/log/maillog saying about each email being denied due to the configuration of sendmail. if your firewall is not an issue then sendmail is blatantly NOT set up fine. never assume things are working properly. check the sendmail howto if you need to sort out a suitable relaying protocol.

I don't know if I understand the problem I am having is not sending mail. I can send mail to anyone on or outside my network. My problem is recieving mail from the internet. I can recieve mail easily from anyone on my network. And as far as I know send mail is only for sending mail not recieving it. I need to know how to recieve it on my computer.

no, like i said you need to check what relay method you are using. i can't remember the actual facts about sendmail off hand but you can specify relaying based on wether an email is FROM someone/somewhere, TO or FROM someone/somewhere or a load of other more complex methods. there are many other things that could be stopping you getting the solution you want, but i think this is the most common. your sendmail may well be wet up to only accept mails from your lan, and reject ones from elsewhere, even if they are addressed to the lan. so you want to check what relay method you have set up in /etc/mail/sendmail.mc and check that with the howto. Like i said tho, look at the logs first, they are there for a reason.

acid_kewpie is right
put domains that can use your sendmail to /etc/mail/access file
put your domain name in /etc/mail/local-host-names

Sendmail sends and recieves mail. What it doesn't is deliver it to the customers (pop3 does that)
so
go to /var/spool/mail/
and check what files are there and how big they are
if your mail is there, then setup pop3 server

i personally use qpopper 4.0 which is available for free at www.eudora.com
once qpopper is compiled you have to start it up with xinetd

Thanks for the feed back. I think I'll have to read through a lot of documentation on sendmail but at least I know where to go now thanks.