The mail server you point to for the Outgoing Mail Settings needs to be configured to "relay" email messages out (e.g. you need to point it to an SMTP Server).
If you're using an internal Exchange environment for your mail you'll need to configure Exchange to have an SMTP server (if you haven't already).
If you're using an external email service like Office 365 or Gmail, you'll need to use their SMTP server to do the relay of messages.
The port is probably the first thing i'd check.
The default protocol for SMTP is port 25...but if your SMTP server is configured to use SSL or TLS, the port will be different. I believe it is port 465 for SSL or port 587 for TLS.
Thanks for your help, I tried 587 and it is connected succecfully.