I'm probably over thinking this, so I'm hoping to get some clarity. But we've had an issue for a while and I can't get my head around it.
When we create a new user, the remote mailbox is created in our on prem environment and syncs to office 365 with dirsync.
We then need to assign a licence, which we use the adaxes licence option when the account is created, which works great.
The account is initially created with a remote rotuting address of $email@example.com.
The onprem then applies the required exchange policy and sets the primary SMTP (we have 2 in our company based on a specific field being set to a specific value), the onprem AD naturally updates the User Logon Name in the onprem AD. But it doesn't replicate to O365.
In fact the UPN on O365 will be firstname.lastname@example.org as the exchange policies obviously aren't applied at O365 level, they are assigned by the onprem exchange.
My guess is that it's because once the licence is assigned DirSync will not change the primary UPN.
So how do I work around this?What's best practise? I thought about excluding hybrid mode completely and ignoring the onprem exchange, from limited testing, the onprem exchange isn't needed for most of our environment now that we're Windows 10/11.