Imap account, Sent folder defaults to Drafts folder on the server, cannot be changed.

I have a problem with my main email, its an IMAP server by my internet provider pt.lu, I discovered the problem because my Drafts folder showed the content of the Spam folder on the server. The problem has been going on since September, I found several sent messages that I wrote and sent on my iPhone or iPad from that period on saved in the drafts folder.

The Sent Folder defaults to Drafts on the server, it cannot be changed. Well I can change it to the Sent folder on the server in setup, mail, accounts, in the advanced tab of the account, but I cannot change Drafts to drafts, it's still greyed out and when I click done and reenter the account settings or check in the mail app, the Sent folder is mapped to Drafts again. I can map the Drafts folder to the one on the device, or to any other, non-assigned folder on the server, that change is applied. However I would rather have my drafts saved in the Drafts folder on the server and my sent mails in the sent mail folder on the server on all my devices. The folder Inbox, Drafts, Sent, Deleted and Spam on the server are system folders, I cannot delete or move them, I've seen that suggestion in several other threads about similar problems.

This problem is on my two most used devices, the iPad Pro 11 (iPadOS 18.1.1) and the iPhone 8plus (iOS 16.7.10), the folders are correct on my older iPad Pro 9.7 inch (iPadOS 16.7.10) and on my PC in Thunderbird.

I did most of my troubleshooting on the iPhone 8plus because I discovered it there, I checked the account settings according to this page from the provider https://support.pt.lu/apple-iphone-mail-email-configuration/ , I deleted the account and recreated it, I deleted the Mail App and the account, restarted the iPhone and reinstalled the app and recreated the account, nothing has worked.