Emails showing in inbox again after deleting

I often have to delete emails multiple times. I may go through my inbox in the morning on the app installed on macOS. And then later in the day I open the Zoho Mail app on my iPhone and many of the emails I have already deleted appear again. This issue appears to happen if I originally delete on my iPhone, they still show up in the app installed on the computer.

This has been an issue for several months and I have just not taken the time to look into it further.

At first I thought the issue was because I was deleting emails from the “Unread” view and deleting from there because they would then be visible again when I would go to the inbox.

I cannot figure out a reason for this behavior so I can only assume it must be a bug in the mail handling in general because I have also seen this problem when using web mail.