Hi there, Grayson_123! We understand that you are noticing a problem where your deleted messages will return to the inbox. We know that keeping your messages organized is important and this is certainly something we can help with.
We’d like to ask you several questions to get started.
First, can you tell us what email service provider you are using? If you sign in with your provider’s webmail, do you see that your messages are able to be deleted as expected?
Do you typically connect your device using Wi-Fi, or cellular data? Do you notice a difference in how your inbox updates after you switch network connections?
Do you use any other devices with this same account? If so, do you notice that you are able to remove these messages using any other devices?
On your iPhone, please open Settings > Accounts & Passwords > Your email account > Your email account again > Advanced. Check the Deleted Mailbox behavior as well as the Move Discarded Messages section. Be sure to restart your device after making any changes here.
We look forward to your reply!
Cheers!