Why did you do this? Port 587 is preferred. Based on what you said, it worked. Also, your description does not mention clicking Update before trying your unsuccessful test. Read Email transactions and reports | Manager.
No. Emails are not sent through any system under the control of NGSoftware. The program sends them through your regular email provider.
Actually, your post was somewhat confusing. Regardless of what may seem safe to say to you, others only know what you write and show. You said you changed from port 25 to 587, then changed back again. But your screenshot shows 587. So it is not clear what the settings were when you conducted your test. And despite all your other detail, you did not mention whether you had clicked Update before any test. Many users have stumbled over this exact omission. I included that comment in hopes of a quick fix.
I also note that Westnet’s web site lists 587 as their preferred port. So once again, I recommend you use that.
Reviewing your forum history, you have reported a number of problems with inconsistent performance of email through westnet.com.au. You have also made negative comments about that provider in the past, going back several years. Taken as a whole, your history suggests problems with your provider. I recommend experimenting with another.
@Cognicom has not been active on the forum since December 2018.
Not sure whether this is related to your issue, but I have found that if an email sent from within Manager is sent to a “proper” mail server, it seems to work everytime, but if sent to one of the web based systems such as Hotmail or Yahoo, then it seems to be very intermittent. I cannot see why this should make a difference as I don’t have the working knowledge for mail servers but it certainly does make a difference.