Airmail app 4 emails in trash won't empty

If anyone is using the Airmail app maybe you can help me with this problem.

I've got 4 deleted emails in the trash that I am unable to delete. The 4 that are in the trash are greyed out and have a gold colored triangle and gold text next to it that says: "Performing sync." I can't empty just those 4. All the rest of the emails in the trash will delete though. I am new to this Airmail app. How can I get rid of those 4 deleted emails that remain in the trash. Anyone else see that?
thanks for a reply....