I took the advice of the Best Practices article and am using my registrar's DNS server instead of my own as the primary and secondary DNS servers.
Here is what I have done up to this point in case it applies to my questions.
My registrar is namecheap.com and this is what their interface for dealing with their DNS services looks like:
I made both the www and @ records A type records and typed in the IP. Obviously I used the actual IP address of my server instead of 1.1.1.1.
Then for the MX record I was suddenly unsure what to put. For the host I decided on mail because that is the sub-domain that I wanted user to use for the POP, SMTP, and IMAP services. For the mail server host name I figured it must be the domain name that I am editing the DNS host records for so I put that in.
I figured that the mail sub-domain needed to be created so I made an A record for it as well. Again with the subdomain fields I was unsure exactly what to put so I made it an A record entered the IP of the server and put mail in the host. Putting mail in the host was only field I was sure about.
Then on my server's DNS panel I added a Zone record with the following:
Zone Name: mydomain.com.
Type: Master
SOA: dns1.name-services.com. (The main name server of namecheap.com)
Admin email: mylogin.mydomain.com.
After doing that a NS record was aparently created with the new Zone automatically. It contained the same server I indicated in the SOA field above.
Now, I created an MX record within the new Zone and put in the following:
Map from: linusadmin.com.
Mail Exchanger: mail.linusadmin.com.
Precedence: 10 (the default)
I also have another mail server that I am going to use as a backup. But I am unsure what that record should look like as well.
At this point I have the Web services working perfectly as far as I can tell.
Thank you again for any help I'm very new to this and appreciate the help I've already recieved.
Jamie