Switched to Windows 10 - email server is being blocked

I have just switched to Windows 10 and my Norton 360 appears to be blocking one of my email servers.

I keep trying to get through to https://airmail.airways.co.nz/OWA/ but I keep getting 'This webpage is not available' even though others are able to reach it. When I went into my Norton 360 security history a block was shown each time I tried to get in.

How can I unblock my email server to allow Norton to let it through?

Thank you,

Colin Davis