On the SMTP server itself you can also run "netstat -a" to make sure that port 25 is listening. If not, you may need to check with IT or networking team to make sure that port is open and listening.
Which other steps in the KB article have you tried? Have you tried sending a test email via SMTP server using non-OSIsoft software? Solution #3 details one possible way using Powershell.
Thanks for your response.
I've successfully connected to our SMTP server via telnet and checked if it is listening to port 25 by executing the netstat -a command; and it was.
It's still weird that we still could not receive test emails.
Could it possible be that the ISP is blocking port 25?