Duplicate email in BB inbox when using Apple Mail

Hopefully someone can advise with this:

I have BIS setup with GMail, my GMail is set to IMAP only, so POP is turned off. When writing or replying to emails in Apple Mail (7.0/Maverick) as soon as I click send I get a duplicate as a new email on my BB sent from myself.

I carried out the steps in this KB: KB10332-Duplicate sent email message arrives on the BlackBerry smartphone when sent using an integrated Gmail account

But it has not helped and it is still happening.

I also turned off 'save drafts on the server' in Apple Mail.

I can't see a reason for this to happen. With no BIS not using POP it should see the sent emails as sent emails, what is it about the behaviour of Apple Mail that causes BIS to send me my sent mail as a new email.

If I send an email using the GMail website, I get the usual sent mail on my device as it should be, certainly not as a new mail from myself. In fact, it obviously means the issue described in the KB is not the issue I am experiencing because it works fine for sending mails from GMail's website.

Hope someone has some insight on this!

Thank you