mail not syncing imap mail read/unread

My Mac Mail is not syncing read/unread mail. I have my own domain through Newtek and after some research and a phone call, it appears to be an issue with mail, not the server side. Does anyone know what the fix is for iMap accounts and Mac Mail showing read/unread syncing? My iPad and iPhone are all in sync. ie, when I read an email on my iPhone, it shows read on my iPad, and vice versa, however, these emails do not show read/unread on the iMac Mail client.

Thank you in advance for your help.