I don’t have any OSX computers that I can try. Have you tried a different program to access your email on the Mac to see if the problem might be related to the email program somehow?
You may have to contact tech support about this one, unless one of the other users has an idea. I’m pretty sure that neither of the other two people who regularly answer questions here uses a Mac. I think we’re all Windows users.
770-582-0004 9 AM - 6 PM Eastern M-F or firstname.lastname@example.org