SMTP Relay email stuck at Queue folder

During my SMTP Relay setup, i noticed the Send email function is called successfully BUT no email is sent to my mailbox. I check the following directory C:\inetpub\mailroot\Queue and noticed that

PowerShell script to test SharePoint Send Mail

Thought it would be good to share some of my script to the public Copy the below script and save as .ps1 file. Run it in SharePoint Management Shell with

#160009: The e-mail address ’emaill address’ is unknown

Bumped into this error when setting Office 365 Relay in my Local SharePoint On-premise server for outgoing email. I have done the following steps -> Ensure you have done the