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.
It has a multi-upload file widget in the node form so you can choose many files at once.
It shows a nice progressbar with the PECL upload progress PHP extention.
The user can choose how long the file(s) should be available on the website.
By default, it is endless as long as there is traffic. The user can limit it to a fixed amount of time.
To prevent deeplinking and the possibility to use the service as a free hosting platform, everything is secured with .htaccess files. PHP files and things like that are renamed to .txt extention for system security.
The website just gives links to copy-paste into your email.