Hello again. The last few days have given me lots of new things to do, so apologies if you are being inundated with blog posts!

So today I went to enable a new Exchange 2013 Hybrid configuration. I used the Start Menu launcher for ‘Exchange Administrative Centre’, which to be honest I don’t usually do. This took me to https://localhost/ecp/?ExchClientVer=15. I then went to Hybrid and enabled the Hybrid Configuration. I logged into Office 365 and was greeted by this friendly message of doom:

This error is quite easily solved; do not use localhost as the server name when you access the ECP. Use your client access namespace instead. For example, if my CAS name was mail.misstech.co.uk, I would browse to https://mail.misstech.co.uk/ecp/?ExchClientVer=15.

Just be sure to put outlook.office365.com and your CAS name into your Intranet Zone too or you’ll then get an error about Cookies!

Thanks for reading!