last logon time Users
Enable attribute Last logon time in get-msoluser to be able to know when a user enters the portal, currently only you can get Access Log, "last logon time", with PowerShell in Exchange Online.
Embry Fedora commented
Yes Shane.. Last logon time reported by Get-MailboxStatistics gives inaccuate value because it also shows the last time when the background tasks like Mailbox Assistant accessed the mailbox. Most of the time, we use lastlogontime to identify users' last activity. You can get users' "Real last logon time"(I mean user's real last activity time) using Get-MailboxStatistics. For more info, refer the below blog.
This is critical to our organization because the lastlogontime in on-prem AD does not get updated when users authenticate with ADFS. And Office 365 is all we use ADFS for.
I have contacted Microsoft and was notified that this exchange mailbox statistic is not accurate.