Queued emails

I'm working with the Gateway mode. FortiMail able to received emails coming from External domains but it is being queued and not able to handover those mails to email server. If the customer suggest to revert back from previous setup (remove fortimail from network). 

Here's my questions now.

1. What will happen for those queued legit emails inside FortiMail system?

2. It will automatically purge after 24 hrs or more?

3. Is there any chance that recipient able to receive or retrieve it?