Deletion of mail account not possible iphone

Hi community,

when I try to delete a mail account (actually two old ones) on my iphone, there is no "Delete" button visible. There is only a text saying something like "The settings of this profile have been installed by the profile xyz Secure Email Setup". I recently deleted other mail accounts from my phone, but there the normal "Delete" button appeared as it should be.

How can I delete these mail accounts from my iphone?

Thank you and kind regards

Oliver