It is possible to add attachments to a message sent via MICE. Think about an image or a document you would like to send along with.
Despite the fact that it is possible to add attachments to a message, we recommend not to but rather include links to the message. Doing this, the chance of the email not being delivered to the recipient's inbox is reduced tremendously. E-mail services regularly hold messages that have too many or too large attachments and mark such messages as spam. Subsequently, these messages will land in the recipient's spam folder resulting in the recipient deleting or never reading the message.
Organisations such as banks and governmental institutes often have set very strict security settings in their mail server to block unwanted files/attachments. So, attachments sent to contacts from these organisations are often flagged and deleted (the email mostly does come through, but without attachments).
We recommend you to add the content of the attachment to your website so you can generate a link to include in the message. This way, you can forward the link more often, easily find back information through your website and maximize chances of your email being delivered to the recipient's regular inbox.