Multipurpose Internet Mail Extensions (MIME)
Email used to be simple. One sent a simple text message to someone else. As email became more widespread people wanted to send files such as data files or documents or spreadsheets to other people. A method called MIME was developed for embedding attachments and other information in email messages.
Attachments are also known as MIME types. MIME stands for Multipurpose Internet Mail Extensions and is the standard used for embedding attachments in an email message. You will see “MIME” or “MIME type” frequently in relation to email attachments, especially in email attachment configuration menus.
There are many different types of MIME attachments and all email clients have some way to deal with them.