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I am very new to Linux and I tring to setup a dedicated
computer to host several services. I have RH 7.1 installed and sendmail works to a point. I can from the local machine
go into ELM and type a message to a user and include the entire domain. The message goes to the proper mailbox no problems. I installed the IMAP RPM to include pop3 service. When I try to connect with my mail client from another machine it downloads the message fine (but after a 15-20 sec. wait) but when I try to send messages it comes up with an error that the SMNP server is not responding. Is there another service that I need? I really don't understand the sendmail.cf to well. I ran a program called install-sendmail-5.5.tar and it set it up to this point.
Also another question that is related. The domain I am on already has a mail server. I noticed that you can send messages leaving off the host name of the machine your sending the mail to(server). Since the other mail server is the same way am I going to have a conflict? To me it looks like there are two mail servers with the same exact @domain.com would cause confusion. What setting will make it where the mail must be sent to the full domain user@host.domain.com.
The pause that you experience when downloading mail might be due to your DNS settings. What do you have in /etc/resolv.conf and /etc/hosts? Have you configured sendmail to relay for the local domain? I don't know where RH will keep the relevant files, have a look in /etc/mail for sendmail.cf and relay-domains . It should be noted that sendmail.cf ain't friendly.
As for the multiple mail servers - the mailserver that is used for the domain is decided by the domain's MX record(s) as per the domain's name server. If you have multiple name servers you simply have multiple entries in your DNS server for the MX records. Each MX record has a value associated with it, this decides which machine is used to relay the mail first, if the first machine is down then the second one will be used. Clearly you need to have the mail end up at the same location at the end of the say so your user's mail client can see it! Off the top of my head I can't remember what happens if you have multiple MX records will the same value... Will look it up for you if you wish.
POP and IMAP are separate protocols. You wouldn't set up a mail server with IMAP so your clients can use POP, you would set it up with POP.
As to the second question, the domain name doesn't need to be there because your DNS service is working properly. If that goes down, nothing works!! There wouldn't be any conflict caused by another mail server on the network so far as I know. It's just gonna be acting as a MTA at that point, and it acts pretty much like anything else when it looks for another machine on the network. No worries AFAIK.
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