How do I secure my email server

[jswilson]

Every day I get a message like this:

--------------------- sendmail Begin ------------------------
Relaying denied:
From [211.206.189.140] to infobank7655@hanmail.net: 1 Times(s)

The IP and email address may change but there always seems to be someone probing my system.
I also get:

--------------------- Connections (secure-log) Begin ------------------
Connections:
Service pop3:
198.64.140.152: 1 Time(s)

The IP address is not one of mine. I don't know what they are doing but I can't imagine they mean me any good.
Question #1: How can I be sure that there is no unauthorized access to my mail server?
Question #2: How do I set up my email server so that it requires Secure Password Authentication (SPA) in Outlook?
I don't consider myself overly paranoid, but everyday since I have got my static IP address someone has been touching my system.

[jasonlambert]

what POP3 Daemon are you running?

You are bound to see hundreds of connection attempts, as spammers scan entire Class A IP ranges at a time looking for badly configured mail servers that will relay their spam.

Really your POP server should be IP restricted if its just for home access, and unless you have a domain that you have set MX records on to point to your mail server, you should proberly ip restrict(firewall off) SMTP as well.

Jason

[jswilson]

I am running RedHat 9.
I have set up the IP restrictions but I do not know if that will block me from accessing mail when I am not at home.
I do not like the idea of sending the user name and password to the mail server in clear text because it is the Linux user name and password as well.

[jswilson]

What settings do I use in TRUST_AUTH_MECH and confAUTH_MECHANISMS to get Outlook to use SPA?