A MX Record identifies the email server(s) responsible for a domain name. When sending an email to user@xyz.com, your email server must first look up the MX Record for xyz.com to see which email server actually handles email for xyz.com (this could be mail.xyz.com - or someone else's email server like mail.isp.com). Then it looks up the A Record for the email server to connect to its IP-address.
A MX Record has a Preference number indicating the order in which the email server should be used (only relevant when multiple MX Records are defined for the same domain name). Email servers will attempt to deliver email to the server with the lowest preference number first, and if unsuccessful continue with the next lowest and so on.
There you would find 4 fields:
- Zone: The domain name for which you setting an MX Record needs to be entered as the Zone. If you are configuring the email server for yourdomainname.com, such that you can receive mails@yourdomainname.com, then you need to leave this field blank.
- Value: This is the email server domain name. If the email servers hosting your domain name are managed by you, then you may set the Value in the format - mail.yourdomainname.com.
- If you are using another Internet Service Provider's email server, then you need to enter a Fully Qualified Domain Name like mail.isp.com. Note that a Fully Qualified Domain Name always ends with a "." in the end.
- TTL: This is the Time To Live for this Record. Any Server which once queries this Record will query it again after this time interval. The ideal TTL is 86400 which is 1 day. It can not be set to less than 14400, i.e. 4 hours.
- MX Priority: An MX Record has a Preference number indicating the order in which the email server should be used (only relevant when multiple MX Records are defined for the same domain name). Email servers will attempt to deliver email to the server with the lowest preference number first, and if unsuccessful, continue with the next lowest and so on.