IIS 5 & IIS 6
SMTP/IIS6 on Windows Server 2016 - Email Just Wont Send
Re: SMTP/IIS6 on Windows Server 2016 - Email Just Wont Send
Jun 14, 2018 05:31 AM|deepakpanchal10|LINK
It looks like it is using a Office 365 to send mails.
Possible that there is some setting related issue.
I suggest you to provide a detailed steps how you set this SMTP.
It will help us to narrow down the issue.
We will try to refer the steps and try to reproduce the issue on our side.