Mail eXchanger Lookup Online or MX Lookup Online gives you a simple interface to get information about mail servers that are responsible for accepting emails within the specified domain. This information is stored in so called MX records in the Domain Name System (DNS).
Each MX record specifies a mail server, its preference value and it also contains the TTL (Time To Live) value. The remote client that wants to send email to an email address within the specified domain will firstly try to contact the mail server with the lowest preference value. If more servers have the same value set, the client should randomly determine their order. The TTL value specifies how long the MX record stays valid. DNS heavily uses cache and it is the TTL value of the record that says when the cached information expires and should be refreshed.
MX Lookup Online is commonly used in case of problems with email delivery. Checking whether the MX records are set up correctly is usually the first step to do.
Enter a fully qualified domain name into the Domain name field. Then click the "MX Lookup!" button and you are done. You will get the list of mail servers and their preference and TTL values.