Nov 04 2020 03:49 AM
Nov 04 2020 08:27 AM
If you have dirsync enabled, you cannot make such changes directly in ExO. Your on-premises AD is the "master" and O365 admin interfaces will always throw a similar error.
The only workaround for this scenario is to use the -WindowsEmailAddress parameter:
Set-Mailbox user@domain.com -WindowsEmailAddress new@domain.com
which will set new@domain.com as the new primary SMTP address, while keeping the old one as secondary. This still does not guarantee that the change will not be overwritten during the next full sync cycle, moreover it's not an officially supported mehtod.
Nov 04 2020 08:29 AM