You may find that you have spam building up in your spam folder and no way to delete it because it is not visible in your e-mail client. In order to make your spam folder visible in Thunderbird follow the simple instructions below.

First right-click on your Digital Crocus inbox and select 'Subscribe'.

Select your spam and virus folders and click Subscribe, then click OK.
You should now see your spam and viruses folders in your folder list and should be able to clear out your spam when required.