Checkmk Werk 11980: check_mail: better error message if email could not be copied

ID: 11980 Title: check_mail: better error message if email could not be copied Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 If a mail could not be copied the resulting error was a raw Exception with the title: "Response from server: SERVER". This werk changes the Exception type to RuntimeError by reusing the function "verified_result".