Mail Server Issues; Can't Send E-mail (using sendmail)
Currently I'm trying to set up an E-mail server. To keep things simple, I'm using a VMWare virtual machine so the "server" isn't yet serving any useful purpose. I'm doing this so I don't try to set up a useful server until I figure it out. I'm also doing this so I don't yet need to concern myself with spam protection or virus protection for E-mail. Of course I plan to implement these features later, but I figure one step at a time. To me, the first step is getting the E-mail server to work.
Currently my virtual machine is using Debian 3.1, and I plan to use Sendmail and Dovecot. I have managed to install both Sendmail and Dovecot. I've gotten to the point of being able to log in to check messages on the mail server via an E-mail client, and it's worked from both the host machine and two other virtual machines, all of which are on the local network (I haven't yet decided to forward E-mail traffic from my router to the faux E-mail "server," since I figure one step at a time.).
Unfortunately, I cannot seem to be able to send E-mails between different accounts on the server. I've set up a couple of bogus accounts on the server so I could use them for E-mail, but I can't receive E-mail. I've tried and failed at sending E-mail between the accounts locally on the server, logging in as each user to see if the message was received. When I try writing a message on an E-mail client on a seperate machine, I get an error stating that the server is either unavailable or isn't accepting SMTP connections. I know the "server" is available because I make sure the virtual machine is running before I try anything (and I can ping the "server").
The thoughts I have are:
Something in the configuration is bad, but I'm not sure what. I've never set up an E-mail server before so it could be any number of things.
Debian *may* have a firewall turned on by default. I don't know. If this is the problem, how do I disable it? Remember, this "server" is a virtual machine that serves no useful purpose, so security isn't a concern right now.
It could be a combination of the above.
Somehow, if the firewall is causing a problem, I doubt it's just that. Remember I can't send messages between the accounts, even if I try to do so locally on the "server," using the Mail program. I know it's not the firewall on the client side, because two of my "clients," also virtual machines serving no useful purpose, don't have firewall software installed.
I'm also using IP addresses directly (when I set up the E-mail clients). The DNS isn't working on the "server" right now. But is that an issue if I use the IP addresses directly? I'll fix the DNS eventually, but I wonder if that'll cause a problem if I don't try to use DNS names?
Right now, my principle concern is to set up the E-mail "server" so it can send E-mail between PCs on the local network. I'm not yet going to worry about spam protection, virus protection, or even DNS. I figure those are things I can worry about setting up and fixing later.