Total email nightmare - need some expert's help please!

Out of blue my 4,000 emails from my Cox email IMAP account (Inbox only) end up in my wife's Cox email account Inbox!? Spent 2 days on the phone with Cox (all levels including Tier 2) Tech Support  and nobody knows how to get them back!!! Forwarding is out of question since allows to move only 8 emails at the time. The Full Recovery backup would get me all emails back to my Thunderbird client email account however they will disappear after syncing to Cox server...
Any hope to fix this mess?