t.mail.smtp.ESMTPSenderFactory requireTransportSecurity fails to recognize when SSL is in use

New submission from jiggle <None>:

If one uses t.reactor.connectSSL() to establish an SSL connection to a SMTP server, and requireTransportSecurity=True, it still attempts to use TLS (over SSL) and usually fails (the server won't allow it).

It should recognize that TLS is already present...

Current work-around is to set requireTransportSecurity=False when creating an instance of the factory.

Failure in this case (from the server, with an SSL connection already present is):
Failure: twisted.mail.smtp.TLSRequiredError: 502 Server does not support secure communication via TLS / SSL


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Type     : defect
Component: mail
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/3989