Does the server support port 587 for sending mail?

Yes - Smarthost servers support port 587 (smtp-submission) for sending mail. Port 587 is intended for sending e-mails by client mail programs, we recommend changing the outgoing e-mail port from standard 25 to port 587. For example, an Orange internet connection users need to change port to 587 to get send mails ability because port 25 is default blocked.