Test unit Mailer test failing Mime-version

my test is failing because of the string: Mime-Version: 1.0\r\n added
to the subject


To: [email protected]\r\n
Subject: test\r\n
Content-Type: text/plain; charset=utf-8\r\n\r\n

expected but was


To: [email protected]\r\n
Subject: test\r\nMime-Version: 1.0\r\n
Content-Type: text/plain; charset=utf-8\r\n\r\n

how can I add the mime version in my test ?

thansk

kad