What is the limitation when using an A-record to define a mail server name?

The main limitation of using an A record to determine the mail server name is that an A record only points to an IP address, not to a specific server role, such as a mail server. For mail servers, an MX record is typically used, which points to the domain name of the server handling mail.

Using an A record directly for a mail server can lead to mail routing issues, as mail clients and servers rely on MX records to determine priorities and proper message delivery. Additionally, MX records allow for flexible changes to server IP addresses without altering client configurations.