Some basic e-mail and web site server questions

Well, I’ve been building Web sites for quite a while now, and I’ve never worried too much about the guts of those machines that actually store the pages I build.

But now I have a situation I’ve never encountered before: My client’s e-mail and web servers are not run by the same people.

In the past, everyone I’ve worked with has had both their e-mail and their web site hosted by the same provider. But this client has their Web site hosted by someone, and their e-mail handled through a MS Exchange server in their own office.

Now comes the problem: I’m going to set up their redesigned site on a different host, one that offers better features, etc. But I don’t want to mess with their e-mail service. What’s going to happen to their e-mail when I submit the new DNS info. for their web site? Anything? Nothing? And how, exactly, does e-mail find its way to their server now?

The DNS host resolves the hits to the domain name, and routes the HTTP hits vs. the email hits, etc. Each type protocol has a different DNS record. The DNS hosting company should allow you to update just the HTTP mapping without touching the email mapping. I haven’t done this for a while so don’t remember the particulars, but your DNS hosting company should have FAQs on its web site for how to do this.

This kind of stuff is done all the time and is no problem at all.

The email routing is handled by their MX (mail exchange) record, which is handled by their nameserver.

As you probably know, when you register a domain name, along with admin and technical contact info, you also have to enter a nameserver (usually two actually). Something like

Whoever runs needs to know that the MX record for this domain will not be or It’ll be whatever IP address or domain name that belongs to the Exchange server in the company’s office.

Imagine the nameserver like a router. Someone sends an HTTP request to their browser to get the web site. The browser gets the nameserver info from the “big list of nameservers” then the nameserver routes the browser to the correct IP based on the domain’s A records. If someone sends an SMTP request, the nameserver routes the mail to the correct IP based on the domain’s MX records.

Just make sure that this new host you’re going to, with “a lot of better features” includes “good customer service” so you can talk to someone about the MX record specifications. Otherwise, you’re screwed.

Mail is resolved through a special type of DNS record called an MX record.

If I have a domain called, and an “A record” for pointing to my web server address, that gets my web traffic handled.

But I may also have an MX record for that points to another address, and any attempt to send mail to any address will send mail to that host.

In fact, I can have multiple MX records with different priorities. If the first priority MX host is down, the attempt will be made to deliver the mail to the second host, and so on.

But the basic lesson is: A and CNAME records are for general resolution of host names; changing them doesn’t affect MX records.