There is no max file size limit that can be sent and received, however, Plesk defaults the limit to 2mb. You can change this in Plesk.
To change this do the following,
- Login to Plesk
- Under Server Management, Click "Tools & Settings"
- Under Mail, Click "Mail Server Settings"
- Change the "Maximum Message size" to however large you would like it to be. (for example: 25600 for 25MB limit or 30720 for 30MB limit)
- Click "OK"
*Also, be aware that some ISP's may block messages over 10-15mb