Google Apps is essentially free email hosting and will allow you to keep all the same email address for your domain. Google's email service has some of the lowest rates of spam and never gets blocked by AOL or large ISPs like some hosting companies like us. It also includes online applications like Google's Spreadsheet and Docs. 

To setup Google Apps for your domain:

1. Sign up for free at http://www.google.com/a/cpanel/domain/new

2. Once signed up and logged in, click "Verify domain ownership" top right.

3. Under "Verify your domain ownership" select "Upload HTML file" from the drop down box. Upload the file to your hosting account following the specific instructions displayed by Google.

4. Login to Manage Domain at http://4domains.com/manage and select DNS Settings at the bottom left. The second record from the top should be "Mail Exchange Preference=0 (MX)." Click modify to the right of this record and enter in ASPMX.L.GOOGLE.COM. (be sure to include the period at the end). Click modify again to finalize the changes.

5. On the main DNS settings screen under the middle "Type" column, click the drop down box at the bottom and select "MX 10." Set the very left field to @ and subsequently add the four additional MX records listed at http://www.google.com/support/a/bin/answer.py?hl=en&answer=33915