Hi @Baylar_Ismayil ,
Welcome to our Q&A forum!
I couldn’t find any official documentation from Microsoft that provides the last logon time information for OWA users only. As far as I know, we can use Get-MailboxStatistics cmdlets to get the last logon time for users. As below:
In addition, I found a thread introduce the way to try using MS Logparser to extract the relevant logon information from IIS logs. For your reference: https://serverfault.com/questions/558215/find-out-if-user-logged-in-to-owa-read-his-emails
Another possible solution is that you can try to enable Audit logging for the specific user, it will record IP address and logon information. See: Want Audit of a specific user logon attempts on to the Exchange mailbox using any client, OWA, Active sync, Outlook etc
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