I've noticed that Thunderbird had a problem where it won't receive emails, for some reason. There's no error message or warning. Emails that I know were sent to me simply never arrive. Below is a simple temporary solution to this problem.

Thunderbird not receiving emails - work around

1. Open your Thunderbird email application.
2. Right mouse click on your email address in the top left corner of the screen.
   
3. Click 'Settings...".
4. Click on 'Server Settings'.
   
5. Now you're in the 'Server Settings' panel. Check the 'Fetch headers only' option.
   
6. Click the 'OK' button.
7. Check your 'Inbox' again (Click the 'Get Mail' button.)
8. You should receive the headers of the emails you couldn't receive previously. The email messages will look like this:
   
9. Click the 'here' link to download the rest of the message.
10. Navigate back into the 'Server Settings' panel like you did above, and uncheck 'Fetch headers only' check-box.
11. Click the 'OK' button.

You shouldn't have any problem receiving emails regularly now. If you do notice that you're not receiving emails in Thunderbird again, repeat the process in this tutorial.