Unable to delete ghost SMTP servers from Mail.app

I am trying to remove some old SMTP server accounts from my Mac, since they prevent me from sending emails from Mail.app. Every time I delete them from within Mail.app, they just reappear. I found the entries in Keychain as hidden entries, but deleting them give the same result - they just reappear.

I am running macOS Monterey, but I am pretty sure I had the same problem on the previous version. At the moment I am just using another non-Apple mail program, but I would prefer to use Mail.app.

Does anyone have any suggestions?

Thanks

Unable to delete ghost SMTP servers from Mail.app
 
 
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