Programatic Access Popup wont go away after disabling in Trust Centre

When trying to email from an application we are recieving the message "A program is trying to access e-mail address information. If this is unexpected, click DENY and verify your anti-virus software is up to date" and you have to wait and then click Allow after 5 seconds. This is extremely anoying for our clients that are sending hundreds of emails. This was happening with Outlook 2003 on a Windows 7 system, I am aware that in later versions we can disable programatic access warning. So we have upgraded both the clients computers to Office 2016 and disabled programatic access warning. But the popups still happen, and it even says Antivirus Status: Valid in trust centre.

I experianced this at another client once before and tried everything and couldnt solve it, put it down to some random Windows issue with that PC and gave up.

But now I know this is a consistant issue, occuring when upgrading Office 2003 to 2016, the office 2016 trust centre settings dont seem have any bearing.

The procedure was uninstall office 2003, reboot, install 2016, reboot, change trust centre settings, reboot > Same popup

Have tried running Office repair utillity, no change, feel like this is some form of leftover registry setting that I need to clear out.

Can anyone point me in the right direction? (Dont need any lectures on Office 2003 being unsupported vulnerable software, we dont control what our clients decide to run)