Problems with AUP reporting on email?

[#1]

For each of the last 5 or 6 weeks I've received "Email AUP exceeded" emails.
On each occasion (as evidenced by usage listings on tickets) I have reduced my usage below the AUP.
HOWEVER each subsequent email is worded as though the matter has not been addressed - "dispite our request to reduce your usage, your usage remains above the AUP" (I paraphrase).
It would appear that reducing usage below the AUP does not clear the 'previously over AUP flag'.
I have also recently culled a lot of email - will check that it was removed from deleted folders on return home; in the meantime can someone please review the week to week AUP transgression reporting?

[#2]

Did you compress compact the folders after deleting messages? The empty space might still count as taken up until compression compaction is done.
Edit: change compress to compact.

[#3]

Surely compression only applies to the local copies of the folders, not the folders on the server?

[#4]

Oops, I meant "compact" to eliminate freed-up space in the IMAP folders.
I've corrected my previous post.

[#5]

David / Jevl (aka spoon whittler),
I did do that on one of my clean up activities, though it is not something I do consistently.  If it has any bearing on PlusNet's assessment of utilisation, then it ought to be included in the advice on reducing email storage size in the very matter-of-fact like email.