Recovered Messages - can't receive email

[Futuresgreen]

Hi all, I tried to send a large file on email, as it was too large, it couldn't be sent.
I can still send email but I can't receive email in Mail on my iMac.

The offending email is in a recovered messages folder below the junk folder.
Ive tried to delete it but it re-appears.
Have tried taking the account offline then deleting, then taking account online but it still re-appears.
I tried using some sumo commands in terminal but that hasn't helped either.

Can anyone help ?

Thanks all.