How to change / delete obsolete SMTP server for mail account on iPad Pro 2020

Thanks to iCloud I was able to migrate most of my configuration from my old iPad to my new iPad Pro.

Even the e-mail accounts were partially migrated, but without the authentication data (passwords).

However, one of my mail accounts shows an obsolete SMTP server as primary server. I cannot delete it, presumably because it is still flagged as primary, but I don‘t find any way to replace it as primary with the current SMTP server (which is also already in my configuration). How can I replace (and delete) the obsolete SMTP server?