Please describe the problem:
Neither deleting email nor emptying the trash removes the physical email files from Maildir storage, it just hides them. This results in massive disk waste over time. The only way to actually delete the physical email files is to select folder->expunge one folder at time. However, in a (presumably typical) maildir set up with hundreds of folders this can take an extensive amount of time.  

Steps to reproduce:
1. Move some mail to a Maildir folder
2. Use various work-arounds described in other Maildir bugs so you can even see the mail
3. Delete the mail
4. Check the physical maildir directory - file is still there
5. Select File -> Empty Trash
6. Check the physical maildir directory - file is still there


Actual results:
The email is hidden from view within Evolution but the corresponding email file is not deleted.

Expected results:
The email should actually be deleted

Does this happen every time?
Yes. 100% of the time. 

Other information:
Workaround. At present, the only work around I've found is to individually select each Maildir folder and then use folder -> expunge. This will force the previously "deleted" email to actually be deleted. What's needed is a function like "expunge all folders" - but this is  what file -> empty trash used to do...