Use local-hostname for HELO command
In the SMTP-HANDSHAKE function, a EHLO command is sent to the server if ESMTP features are required and HELO otherwise. The EHLO command was followed by the value of LOCAL-HOSTNAME, whereas HELO erroneously used the result of USOCKET::GET-HOST-NAME directly.
This leads to the HELO command being rejected, since USOCKET::GET-HOST-NAME does not return a FQDN. With this fix, and an explicit :LOCAL-HOSTNAME keyword argument given to SEND-EMAIL, e-mails go through normally.