By looking through the smtplib module code I think I've found a
potential issue in the SSLFakeFile class code since there's a while loop
which is supposed to be stopped only when the "\n" character is encountered:

        def readline(self):
            str = ""
            chr = None
            while chr != "\n":
                chr = self.sslobj.read(1)
                str += chr
            return str


The patch in attachment just adds a break statement to prevent the while
loop to hang forever in case the "\n" character is never encountered.