Mweb mail issues outgoing mail iPhone

Really struggling to setup an Mweb mail address in my iPhone (X) mail (outlook app has same issue). Cannot send mail, it leaves then I get a prompt that the server did not recognise one of the recipients email addresses and moves it to my outbox.

Have tried many different settings, turned off ssl, and domain names user and password are definitely correct.

anyone had this problem ? I have many friends with Mweb accounts and iPhones that haven’t had any issues.

thanks 🙏🏻