You're ready to send the file but the recipient's email system is not equipped to deal with large files? Mozilla Thunderbird 13 makes it easier to transmit big files reliably: it integrates with file sending services (YouSendIt so far) and can upload documents automatically.
Speaking of integration, Mozilla Thunderbird now can help you set up a domain and email account, too.
›› Mozilla Thunderbird is a fully featured, secure and very functional email program and RSS feed reader. It lets you handle mail efficiently and with style, and Mozilla Thunderbird filters away junk mail too. (Windows, Mac, Linux)