Hi Willy5116,
Regarding deleting messages in the Mail app, does it only occur with a specific account or any? Also, when checking your settings are you seeing the advanced option is set to move messages to the trash or archived. The steps below found in the article here can help you check. Delete emails on your iPhone or iPad
"Set Trash or Archive as your default option
Depending on the type of email account you have, you might see Archive instead of Trash when you try to delete emails. You can edit where your deleted messages go in your Mail settings:
- In the Settings app, tap Mail.
- Tap Accounts.
- Tap your account.
- Tap your account once more.
- Tap Advanced.
- Select Deleted Mailbox or Archive Mailbox to send discarded messages there."
Keep us posted on the information, and provide us with any other steps you've attempted thus far. For example, a normal restart of your iPad or checking additional settings for your mail account.
Cheers.