Troubleshooting “Mailbox unavailable. The server response was: Access denied - Invalid HELO name” when sending email with SmtpClient

Question

I have been trying to send an email by C#. I have Googled for various examples and have taken bits and pieces from each and from the standard code which everyone would most

Answer 1

In my case, it was a wrong port. The configuration provided by the hosting didn't worked both SSL (465) and no SSL (25). I used MS Outlook to "crack" the configuration, and then copied to my application. It was 587 SSL.