read the article and then go talk to Powermta as they will know how their client software is implemented
I have shown you that using STARTLS correctly with that server lets you interact with the SMTP Component. Why it doesn’t work for Powermta is not something I can or will troubleshoot (that’s why they have support for their product and people who know how to configure it)
they might suggest you use a different SMTP service from microsoft
Andrei