IMAP Server with Duplicate Emails but only 1 in Mail - How happened? How to fix?

I host all my domain email at an outside vendor (Rackspace).  I was running up against a hard limit of 25gb in a mailbox, and went into Rackspace webmail to figure out where all my space had gone.

I discovered that the server has in some cases a couple dozen or more of the exact same email stored in each different file (mail being sorted on my computer using Apple Mail rules).  However each email account only shows ONE copy of the duplicated email - even after rebuilding.

Tried:

• Rebuilding each folder - no effect
• Removing all the "visible" emails in each folder to a different folder, and returning - no effect
• Mail count in a folder might be 107, but when moving to a different folder shows 340?  Including the duplicates apparently
• Headers on the duplicated emails look exactly the same
• Number of duplicates shows no rhyme or reason - not by date or age, for example
• Complete reindexing of all the email on an iMac didn't solve the problem

Rackspace says "it's your email client problem", not us (of course)

Rackspace says all the duplicates need to be removed manually (this will take hours)

Any thoughts?  

Brian