Quick post: find users who have an Exchange Online mailbox

If you have a hybrid Exchange infrastructure, it appears that you can query your local Active Directory to find out users who have already been migrated to Exchange Online.

Thanks to the attribute named msExchRecipientTypeDetails (values detailed here), you can find these accounts with a remote mailbox.

Here’s a small function that leverages this msExchRecipientTypeDetails attribute:

	Function Get-RemoteUserMailbox {
	[CmdletBinding()]
	Param(
	[Parameter()]
	[string]$SearchBase = "$((ActiveDirectory\Get-ADDomain).DistinguishedName)",
	[Parameter()]
	[int32]$ResultSetSize = 10000,
	[Parameter()]
	[string]$SearchScope = 'SubTree'
	)
	Begin {}
	Process {
	$HT = @{
	Filter = 'msExchRecipientTypeDetails -eq 2147483648'
	SearchScope = $SearchScope
	ResultSetSize = $ResultSetSize
	SearchBase = $SearchBase
	ErrorAction = 'Stop'
	}
	try {
	ActiveDirectory\Get-ADUser @HT
	} catch {
	Write-Warning -Message "Failed to query AD because $($_.Exception.Message)"
	}
	}
	End {}
	}

view raw Get-RemoteUserMailbox.ps1 hosted with ❤ by GitHub

You can even bind cmdlets like this for example:

Get-RemoteUserMailbox  |
Get-ADUser -Properties AccountExpirationDate | 
Out-GridView

Nice, isn’t it? 😀