This question only affects people who are unable to delete mail via the web interface when their account is 100% full.
It is easier to answer this question by showing how the system puts mail into the "Trash" folder:
1. Select email to be deleted.
2. Copy email into "Trash" folder.
3. Remove original copy of email.
The problem is between steps 2 and 3 two copies of the email exist (the original email and the new copy in the "Trash" folder), if you are over quota this is not possible (you do not have space to create a second copy in the "Trash" folder) and hence the problem.
The solution is to turn off the "Trash" folder when you are over quota, delete some email, then turn it back on.
To turn off the "Trash" folder:
Select options from the top menu bar
From the options menu select "Folder Preferences"
Find the section headed "Special Folder Options"
Use the drop down box next to "Trash Folder", select "[Do not use Trash]"
Press the "Submit" button at the bottom of the page.
Your "Trash" folder is now turned off and you can delete email.
Remember to turn the "Trash" folder back on when you have finished deleting mail.
