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DNS and MX how do they work?

Posted: Thu May 24, 2007 3:31 pm
by alex.barylski
I have been trying to get a mail server setup on my host so I can offer clients email, but after much consideration I've decided to scrap the idea of hosting both mail and web sites on the same server. I'm running out of time I need something now and because I figure security, keeping two essnetial systems on seperate machines mitigates risk.

My web host I have pretty much setup the way I want, using name-based virtual hosting to server several sites with unique domains.

I am now looking into hosted email services and/or possibly renting another dedicated host and having someone setup a mail server.

Is what I want to do possible?

How does DNS work in this regard and how does MX come into play?

I use my hosting companies DNS records - which I pointed my registrar to already. Easy.

If I have one server which handles all HTTP requests for domain.com how do I get a entirely different (possibly remote) server to handle receiving and sending of emails?

If the DNS points to my web host server how does any email know that sales@domain.com should actually goto my second server, not the web host server?

Do I have to use an MTA still on my web host server and redirect email to the other server? Or is this where MX records come into play?

DNS and MX I understand are related but seperate. You can have a DNS with MX but not visa-versa??? You need a domain (DNS) before you can use email (MX) anyways, correct? Thats my reasoning anyways.

Can someone shed some light on how this is possible and what steps, etc I might need to take in order to get something like the above setup?

Cheers :)

Posted: Thu May 24, 2007 3:49 pm
by timvw
Well, just like you configured A and CNAME records in your dns server for 'regular' purposes... You can now add MX records (these will only be used for e-mail puproses..

Basically, you can have an A record that says example.com is at 123.456.789.123,
and at the same time you can say that the MX (mail-exchange) for example.com is handled by 321.987.456.123...

You can even add a 'priority' (lower means more reliable) to the MX record..
example.com. MX 123.456.789.123 5
example.com. MX 123.456.789.321 10 <- in case the host with priority 5 can't be contacted, this one will be used as backup

(An article like http://bobcares.com/article3.html will probably clear things up...)

Posted: Thu May 24, 2007 5:38 pm
by alex.barylski
Cool, thanks for the linkage there timvw. I'll look into it.

One problem though, DNS is a scary beast, so I used my hosting companies DNS. Does this mean I have to setup a DNS locally now? :?

Otherwise each time I add a domain to my server and associated emails I would have to ask my host to add the appropriate MX records?

Thanks again

Posted: Thu May 24, 2007 6:07 pm
by nickvd
Does your host not give you the ability to edit your own Zone Records?

Posted: Thu May 24, 2007 7:14 pm
by alex.barylski
nickvd wrote:Does your host not give you the ability to edit your own Zone Records?
I have no idea...it's a dedicated host so I have full control over my server but I use their DNS. Would the zone records not be on one of their machines? I will login in quickly and see if there isn't something like that in the admin.

Edit:

Ok Sweet. My admin panel does allow me to tinker with DNS stuff. Now I just need to figure it out and get another server setup for email. :)