         # File lib/protocols/smtpclient.rb, line 188
    188:                 def invoke_starttls
    189:                         if @args[:starttls]
    190:                                 # It would be more sociable to first ask if @server_caps contains
    191:                                 # the string "STARTTLS" before we invoke it, but hey, life's too short.
    192:                                 send_data "STARTTLS\r\n"
    193:                                 @responder = :receive_starttls_response
    194:                         else
    195:                                 invoke_auth
    196:                         end
    197:                 end