MX records are stored in the Domain Name System (DNS), which is a hierarchical distributed database that is used to translate domain names into IP addresses and other information. You can use this tool to find the MX record for a particular domain. This tool is available for free on the internet and allow you to enter a domain name and see the MX record for that domain.
For example, you could use a tool like this to find the MX record for the domain:

1. Open a web browser and go to a DNS lookup tool, such as GradeMyEmail.
2. In the tool's search field, enter the domain name for which you want to find the MX record, such as Example Domain.
3. Click the search or lookup button to perform the DNS lookup.
4. The tool will display the MX record for the domain, including the priority of the mail server and its hostname and IP address.

You can use this information to determine which server is responsible for handling email for the domain and to configure your own mail server if necessary.

In an MX record, the priority is a numerical value that indicates the preference or priority of a particular mail server for a domain. When an email message is sent to a recipient at a particular domain, the sender's mail server looks up the MX record for that domain to determine which server should receive the message.
If there are multiple MX records for a domain, the mail server will try to deliver the message to the server with the lowest priority number first. If that server is not available, the mail server will try to deliver the message to the next server with the next lowest priority number, and so on. This allows a domain to have multiple mail servers, with each server having a different priority level.
For example, let's say a domain has the following MX records:
MX 10 mail1.example.com
MX 20 mail2.example.com
MX 30 mail3.example.com
In this case, the mail server would try to deliver the message to mail1.example.com first, because it has the lowest priority number (10). If that server is not available, the mail server would try to deliver the message to mail2.example.com, and if that server is not available, it would try to deliver the message to mail3.example.com.
The priority value is important because it allows a domain to specify which mail server should be used as the primary server for receiving email, and which servers should be used as backups in case the primary server is not available. This helps to ensure that email messages are delivered reliably and efficiently.

Some common errors that can occur with MX records include:

1. Incorrect or missing MX records: If the MX records for a domain are incorrect or missing, email sent to that domain will not be delivered.
2. Invalid syntax: MX records have a specific syntax that must be followed, and any errors in this syntax can prevent email from being delivered.
3. Incorrect priority values: MX records have a priority value that determines the order in which mail servers should be tried if one is unavailable. If these values are incorrect, email may be delivered to the wrong server.
4. Pointing to a non-existent server: MX records should point to a valid mail server that is able to receive email for the domain. If the MX records point to a server that does not exist or is not configured to accept email for the domain, email will not be delivered.
5. Inconsistent MX records: If there are multiple MX records for a domain but they do not all point to the same set of servers, this can cause confusion and prevent email from being delivered correctly.
6. MX records with a high time-to-live (TTL): If the TTL for MX records is set too high, it may take a long time for changes to the MX records to take effect, which can cause delays in email delivery.

If you are experiencing issues with your MX records, it is important to carefully review them and ensure that they are correct and consistent. You may also want to check with your email or DNS provider for additional assistance.