get user login reports in office 365

Hi @francesco falanga

Welcome to the Microsoft Q&A platform!
I will be using a user who has not logged in for 7 days as an example, you can try the following script:

$cutoffDate = (Get-Date).AddDays(-30)
$mailboxes = Get-Mailbox -ResultSize Unlimited
$inactiveUsers = @()
foreach ($mailbox in $mailboxes) {
    $lastLogonTime = (Get-MailboxStatistics -Identity $mailbox.Alias).LastLogonTime
    if ($lastLogonTime -lt $cutoffDate) {
        $userInfo = New-Object PSObject -Property @{
            DisplayName = $mailbox.DisplayName
            UserPrincipalName = $mailbox.UserPrincipalName
            LastLogonTime = $lastLogonTime
        }
        $inactiveUsers += $userInfo
    }
}
$inactiveUsers | Export-Csv -Path "C:\InactiveUsers.csv" -NoTypeInformation
Write-Output "succeed：C:\InactiveUsers.csv"

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