I delete emails from my inbox andthen delete from the "delete" file but within hours, they all return. I have even seen emails 2 and 3 months old comeback to my inbox.
Obviously, what I believe I am deleting from my computer is not being deleted on the server where they are stored.
What can i do?
My wife has had the same problem. Her primary mail reader is on an iPad running iOS 9.3.5 (the last version for her hardware). The iPad is set to delete the messages from the server when the Deleted mail folder is emptied.
The only way the messages are actually deleted from the server is by using our windows10 desktop computer that runs Windows Live Mail. She selects all messages there, deletes them then empties the deleted items folder. All I can say is that something is not playing nicely together... Hope this helps you.
I wound up revisiting this again today as a result of a pop3 mail authorization problem. (ref: POP3 mail authorization, elsewhere on the forum)
Through a Verizon support agent, the DHCP lease was terminated and system reset. After this, our router was reset by switching off the power for longer than 15 seconds. Following this, normal pop mail returned. We also found that when emails in the trash folder were deleted or trash folder emptied, those messages were now removed from the server. The apple mail client all along, had been set up to retain messages on the server until purged from trash.