What is MAPI?

Messaging Application Program Interface (MAPI), is a Microsoft developed application interface for Windows applications. MAPI enables applications to send emails and add attachments.

For example, within Microsoft Word, it is possible to share a currently open document by emailing it as an attachment to a new email. When this option is chosen, the systems default email client will open a new email window (even if it is not running), with the file already attached. All the user needs to do at this stage is add the recipient email, a title and any other body text they require, and click send.

However, MAPI only works if the system default email client has in built MAPI server capabilities. Note that if the email client is not running when a MAPI call is made, it will start and remain running once the email has been sent.