Old ... (OLD!!!) deleted messages reappearing in Inbox

Hi,

I recently had to re-enable auto-fetch on two of my (3) email accounts ... I worked that out ok, I think.

Since that time, in one of the accounts, I have had _several_ _thousand_ _deleted_ emails (from 2014/2015/etc) turn up in that account's inbox - several times - which is to say that I deleted those messages (again and again!) only to have them reappear when next I access that inbox.

The 3 accounts I have configured are:
chris@chriskelly.com.au --- no problem here
subs@chriskelly.com.au --- PROBLEM WITH THIS INBOX
notchris@chriskelly.com.au (catchall) --- no problem here

When is a deleted email _not_ a deleted email ???

Any ideas, please?

Chris