Mx records -
A mail transfer agent or MTA (also called a mail server, or a mail exchange server in the context of the Domain Name System) is a computer program or software agent which transfers electronic mail messages from one computer to another.
An MX record or Mail exchanger record is a type of resource record in the Domain Name System (DNS) specifying how Internet e-mail should be routed. MX records point to the servers to send an e-mail to, and which ones it should be sent to first, by priority.
In order to check the MX record for a domain using Windows, first open a command prompt window (click Start->Run, then type cmd).
A command prompt window will appear, type nslookup and hit enter. Then type "server <DNS>" (such as ns1.serverdomain.com) and hit enter. Then type "set type=mx" without quotes and hit enter. Then type the domain name such as w3courses.com and hit enter. The mx record will then be displayed.
Enter Email Address to check existing mail servers (MX Records)
check the mail server
exist & accepting email address for the given email address. this tool doesn't check the valid email address or not.