The STARTTLS protocol suggests that the EHLO (aka "Hello") message be re-sent after the secure channel has been negotiated, in which case the server should completely ignore anything it learned in the first (unencrypted) EHLO message. However, most servers do not actually require it, and prior to 5.1(124), EMAILX did not send it. Starting with 5.1(124), EMAILX automatically re-sends the EHLO via the secure channel, unless the SECUREHELLO option is specified in the config file as 0, N, or F (i.e. zero, no, or false). That would be necessary only if the server was unable to handle the re-send EHLO.
