eMail do not delete

Email does not delete on iphone or ipad but does when I delete it from my iMacs...

My main email is a POP account throught Brighthouse Networks. I have my two iMacs, my iphone and my ipad set to send and receive messages through this account. When I delete messages from my imacs, the messages get trashed and go away. However, the same exact messages continue to appear on the ipad and the iphone as if I had never read these before and I then have to delete them all over again. Ridiculous.

This email annoyance does NOT happen with my iCloud account or my Gmail account because deleted messages are 'deleted'. What's the magic trick short of getting rid of my ISPs email accounts?

Anyone have a solution, please? Thanks in advance!