MX records are also commonly also known as the Mail Exchanger Records. When people refer to Mail Hub, Postoffice or Mail Host they are referring to the machine that the MX Records point to. That machine's primary job function is to receive mail.

Where is the MX Record Stored?

The MX record is stored in DNS and specifies which mail server is responible for accepting email on behalf of the domain. A domain can have one to many different mail servers. Each mail server is given a preference value to prioritize email deliverly. The lowest preference value indicates the most preferred mail server. When email is received, it tries each mail server in order until one of them accepts the email. A lot of companies who have multiple mail servers use the same preference value in attempts to load balance their mail servers. The reason for this is because most mail programs will randomly choose an MX record to use if they have the same preference value.

How Do I Set Up My MX Record?

First, use our MX Lookup Tool to determine if you have an MX Record already set up. Most hosting providers set this record up for their customers. If you don't have an MX Record you will need to access your DNS controls or ask the hosting or domain provider to add it for you.

Setting	Value
Record Type	MX
Domain Name	Your Domain Name
Priority	10 (or any integer)
MX Record	The Mail Server
TTL	14400 (Time to Live - Which means the information is cached for X seconds, before it's refreshed from an authoritative server)

Here's and example of our how our settings look, which you can verify here: Our Settings

Setting	Value
Record Type	MX
Domain Name	unlocktheinbox.com
Proirity	10
MX Record	mail.unlocktheinbox.com
TTL	14400

If you have difficulty creating or updating your MX records contact your domain provider for assistance.

Source: Unlock The Inbox