This is quite a basic tool to provide a free service to share large files and to cope with the limitation of regular email attachments.
The general email attachment limit is 10MB, but nobody knows that 2MB is overhead in the MIME encoding.
So it is advicable to send up to 8MB at maximum via a regular email attachment.
emailattachment.net limits you to 1GB per file, so you can even share large movie files and big ZIP files.