Question about Domain and Host name fields.

Question

Hello! Just a quick question, I currently have the Mail Server up and running although I'm a little unsure about what exactly needs to be entered into the users email application.
I've tested POP and IMAP using the information that I entered into the "Domain Name" field, and into the "Host name" field, and everything worked great.
Example:
Incoming Mail Server: mail.example.com
Outgoing Mail Server: smtp.example.com
Although while setting up another site and including the normal mail setup via DNS I've also noticed that I can send and receive email by using other sites that belong to me, as long as they are pointing towards our server.
Example:
Incoming Mail Server: mail.mynewsite.com
Outgoing Mail Server: smtp.mynewsite.com
So, I guess my question is whether its bad to use other websites in the incoming and outgoing mail server fields, or should I stick to the incoming and outgoing sites that I have listed in the Mail Server's 'Domain Name' and 'Host Name' fields?
I hope that made sense, thanks again for your help.
Paul
PowerMac G5, Xserve G5, and PowerBook G4 Mac OS X (10.4.8)

Answer 1

Does it matter if our users type mail.example.com
into the incoming mail server, or are they allowed to
use their own domain name "mail.mydomain.com" as long
as the DNS is setup correctly?
There is no intrinsic 'meaning' to hostnames entered into the mail client. These are merely converted to IP addresses, using available dns, and then the mail client communicates with the IP address, using whatever port number is applicable for the service required (e.g., port 25 for smtp, port 110 for pop). So you could use the hostname woohooo.mydomain.com for the smtp or pop server, as long as it resolves to the correct IP.
This enables laptop users to have the one smtp/pop hostname, with lan dns resolving it to the local private IP and ext dns resolving same hostname to wan IP.
There is also no need to have two separate hostnames for pop and smtp. These are typically used by ISPs because they have separate servers doing each job - one doing pop, one doing smtp. If one server does both (and there is no likelihood of splitting the services later) then just the one hostname for pop and smtp is fine.
-david