The contents below are from a Knowledge Base article of Chris/DJB.
You need to check all of the e-mail features in cPanel, configure and enable them before they will work for you. If you don't do this, you'll be hit with loads of spam. For example Spam Assassin is set off by default. It has to be enabled to work for you. You also have to set up the filters.
Also note that the default webmail address you receive should not be used as an e-mail account. This account is meant to catch e-mails that have been misdirected to your account. The default account is an opportunity to get rid of these e-mails permanently. For using the e-mail account feature, you need to create new e-mail accounts. One trick if you are concerned about spam, is to limit the size of the e-mail accounts. I've got mine limited at 25MB, but one could go smaller than that as well.
Here are the steps to follow when you have received a new hosting account:
You need to check all of the e-mail features in cPanel, configure and enable them before they will work for you. If you don't do this, you'll be hit with loads of spam. For example Spam Assassin is set off by default. It has to be enabled to work for you. You also have to set up the filters.
Also note that the default webmail address you receive should not be used as an e-mail account. This account is meant to catch e-mails that have been misdirected to your account. The default account is an opportunity to get rid of these e-mails permanently. For using the e-mail account feature, you need to create new e-mail accounts. One trick if you are concerned about spam, is to limit the size of the e-mail accounts. I've got mine limited at 25MB, but one could go smaller than that as well.
Here are the steps to follow when you have received a new hosting account:
1. Click on the Mail icon in your CPanel. You will be taken to the Mail Manager Main Menu screen.
2. Click on Default Address; Select Discard the email while your server processes it by SMTP time with an error message. Click on change.
3. Click on Spam Assassin.
4. Click on Enable Spam Assassin.
5. Once cPanel indicates the change was processed, click on Go_Back link to go back to Spam Assassin menu screen.
6. Click on Configure Spam Assassin. You will be taken to the Spam Assassin Configuration screen.
7. Change rewrite_subject to 1
8. Click on Save.
9. Once cPanel indicates the change was processed, click on Go_Back link to go back to Spam Assassin Menu screen.
10. Click on Go_Back again. You should now be back at the Mail Manager Main Menu screen.
11. Click on E-mail Filtering.
12. Click on Add_Filter. You will be taken to the Add Filter screen.
13. Type Yes in the empty box. Select Spam Assassin Spam Header and begins with .
14. Click on Activate.
15. Once cPanel indicates the filter was added, click on the Go_Back link to go back to the Filter Maintenance screen.
16. Log out of cPanel.