ZF-10758: Support StartTLS for sending Mails via SMTP


Zend_Mail_Protocol_Smtp supports SSL and TLS, but not StartTLS (see contrstructor of Zend_Mail_Protocol_Smtp)

More information about StartTLS * http://en.wikipedia.org/wiki/STARTTLS * http://www.sendmail.org/~ca/email/starttls.html * http://tools.ietf.org/html/rfc3207


My SMTP pipelining patch (ZF-8528) implements parsing of the EHLO keywords which would allow detection of STARTTLS support. Awaiting application of ZF-10741 to trunk and then I will refactor ZF-8528 out to split out a patch specifically for EHLO keyword parsing. Then this one will be easier to implement.