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My company has only one MX record advertised to the Internet. If the machine that has the MX record tied to it goes down what happens to email destined for us? Do the sending server’s queue email destined to us for at least 24 hrs or does email go instantly back to the sender with a reject message?
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My company has only one MX record advertised to the Internet. If the machine that has the MX record tied to it goes down what happens to email destined for us? Do the sending server’s queue email destined to us for at least 24 hrs or does email go instantly back to the sender with a reject message?

Is a secondary MX record necessary

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.

Email Servers

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.