To whitelist in Thunderbird, you will need to add clark@expattaxonline.com to your address book, and then set up your Thunderbird Junk Mail Controls to whitelist your address book.
1. First, if you find email from clark@expattaxonline.com in your Junk folder, right-click on our email and choose “Mark as Not Junk”
2. Next, click the Address Book button
3. Highlight the Personal Address Book
4. Click on “New Card”
5. In the “Contact” tab of the new card, copy and paste clark@expattaxonline.com to the email dialog box
6. Click “Ok”
7. Next, to whitelist your address book, select “Tools > Junk Mail Controls” from the drop down menu
8. Update the “White Lists” module under the “Settings” tab by selecting “Personal Address Book” from the drop down menu, and then check the box next to “Do not mark messages as junk mail”
9. Click “Ok”