OK. That rules out the obvious cause of what you are seeing, provided you have checked your public IP correctly. And I will take it that you have done so.
The fundamental fact is that Outlook of all varieties works perfectly well with VM's mail system unless there is something about the way you have configured it which is not right.
I'll point you to the correct settings for this program and you should check yours carefully against them.
Do you know the difference between POP and IMAP? They are both the way the program works to collect incoming mail. SMTP is the set of rules that governs the way mail is sent. Don't confuse incoming with outgoing settings. You can chose POP or IMAP but you can't switch between them. The difference between the two is that basically POP only handles one device at a time and with IMAP you can see your e-mail on all your devices and what you do on one is immediately reflected across all of them
So here are the settings:
https://www.virginmedia.com/help/virgin-media-configure-email-settings
However if you find that your SMTP send settings are correct we are back to square one. You will have to run Outlook logging and inspect the log file to look for the VM error code. That is the only way we will ever know what is causing the problem.
I've already given you the link on how to do that. So read the guide on how to do it and get ready to try again.
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