Email wasn't designed for sending files, and does it poorly at best. Most email providers limit the size of the emails (including attached files) to 5-10 megabytes, bouncing back anything larger. Corporate email servers usually limit mailbox sizes too, so large attachments can fill them up quickly.
Here are our recommended alternatives (all free):
* If the person is inside your organization, save the file to a networked server location, and email them where to find it.
Outside your organization:
* If you occasionally need to share large files, use Slingshot's own FileSender.slingfive.com.
Just upload the file and email your recipient a link to download it.
Similar alternatives: www.filemail.com or send.firefox.com
* If you often need to share large files, create an account with www.onedrive.com.
More setup, but also gives you 5 gigabytes of permanent storage with no pyramid schemes and can sync files with your computer or phone.