Deleted emails keep coming back

[#1]

On my iPad when I delete emails they return a day later and emails deleted as far back as February. Any ideas why this would be.

[#2]

When you're deleting the emails on your iPad, have you checked if this is actually deleting them from our server. Try logging in to webmail at https://webmail.plus.net/ and check if the emails remain here when you delete them from your iPad.
If they are remaining on webmail, it's likely your iPad is re-syncing and retrieving the emails you've already 'deleted' previously.

[#3]

Are you using POP3 or IMAP to retrieve the emails on the iPad?

[#4]

The emails do not appear in the Deleted Box on the Server. I don't really understand the second sentence.

[#5]

I am using IMAP to retrieve emails.

[#6]

I omitted to say that the recovered emails do not appear in the Webmail Inbox.

[#7]

What action do you have configured for when emails are deleted? The normal action would be to move it to the Trash folder.

[#8]

On my iPad it is configured to go to the Trash Folder. There are 2 options,  "On My iPad Trash" or "On the Server Trash". I have now picked the Trash Folder on the Server and deleted a couple of emails. These now show up in Web Mail. I will try shutting down the mail on the iPad and see if it recovers them.