Outlook web app is out of date

Issue: you try to login with office 365 homed mailbox, from the on-prem login url and you get the error " your OWA is out of date"

Resolution: Check the remote mailbox properties and ensure target address is set with the correct address. You can also use powershell to fix by typing

set-remotemailbox -id test -remoteroutingaddress test@o365test.onmicrosoft.com

the alias must be an onmicrosoft.com alias​