This is a reply to a very old post, but gmail didn't work for me. It appears that they've changed their setting.
I found a way to do this through a 3rd party (smtp2go.com). You can sign up for a free service for 20 emails / day. That was more than enough for me - I don't scan that many per day. If you use it very often, you can sign up for $5 / month.
Here are the steps:
1- Go to smtp2go.com and get a free account
2- Authenticate your email
3- Go to "myaccount" in the profile page. You will see the smtp server name and username.
4- Now connect to your printer. (You will need to know the printer's IP address)
5- Go to preferences > Email Server
6- Fill up as follows:
EMAIL SERVER SETUP
Return Email Address: <Enter an email address here>
SMTP Server: <Enter the server name used by smtp2go. See step 3 above>
SMTP Port: 587
EMAIL SEND AUTHENTICATION
Send Authentication: SMTP AUTH (AUTO)
SMTP Login Name: <The login name in smtp2go>
SMTP Password: <The password in smtp2go>
7- Leave POP3 section empty
Good luck.