Records mean that the data must be in a structured form. Today, there are almost 2 billion websites on the internet. When you enter a domain name in your browser search bar, you instantly land on a specific page with a single click. With over four billion internet users worldwide, someone can imagine the number of queries served on the internet per second. How each person lands on that specific page, which he/she queried for? Or how your email lands on the particular email address that you mentioned in your recipient email address?
All that is happening due to DNS records; in other words, these are the mapping files that route the internet traffic to the correct destination.
DNS MX record is the mail exchange DNS record that routes the email to the correct destination/email server. It tells which mail server is responsible for receiving the email messages for that specific domain and how your email message should be routed following the Simple Mail Transfer Protocol (SMTP).
The process is simple: when the user sends an email address. The MTA (Message Transfer Agent) software initiates the step by sending the query to identify the MX record. If the MX record is present, it establishes an SMTP (Simple Mail Transfer Protocol) connection with those mail servers, as per their priority.
Suppose there are two MX records for domain abc.com
The number at the start represents the priority hierarchy. First, priority will be given to the lower number. The server will first try mail1 to send the email. If it fails to send an email, then it will move towards mail2 for sending an email.
So, proper configuration of MX record for getting the email is quite essential. If your MX records are not correctly configured or wrongly configured. Then you will not receive an email, or your email will route to the wrong destination respectively.
You managed your MX records, where your DNS records are managed. Like CNAME records, an MX record must always point to another domain, but MX records cannot point to CNAME. That is invalid and will cause a problem.