Why don't MX records point to ip address?

  YinHoNg 10:30 20 Jul 06

Hi. I've been trying to learn about the internet infrastructure recently and i came across the DNS (Domain Name System). I noticed that the A record points to an actual ip address e.g. click here points to 555.555.555 but the mx record points to host name e.g. mail.mydomain.com

Why is it neccessary for the MX record to point to a host name. Wouldn't it be easier if it pointed directly to an ip address?

  Forum Editor 11:11 22 Jul 06

The A record stores an IP address associated with a domain name, but a MX record is critical to the SMTP part of the mail delivery system, and can't exist unless there is first an A record.

When you send an email it goes from your E-mail client to an SMTP server. The SMTP server checks for the MX record of the domain in the E-mail address. The MX record is a domain name, so the SMTP server then gets the A record, finds the IP address, and connects to the mail server.

  Forum Editor 11:18 22 Jul 06

that MX records enable multiple mail servers on a domain.

When a mail server does an MX lookup for a domain name it gets a list of servers and their preference numbers. It will try the MX record with the lowest number first, and if that's unsuccessful it will go through the list of servers until it finally delivers the message or is rejected - perhaps because a particular mailbox doesn't exist on the server.

  YinHoNg 11:26 22 Jul 06

But what if the MX Record pointed directly to the ip address where the mail server is located? Wouldn't that save time since you wouldn't have to look up the a record that the MX record currently stores. You can just go directly to the ip address?

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