Get-Mailbox

Exchange Online: Lists mailboxes

Script

#Requires -Version 5.1

[CmdletBinding()]
Param(
    [switch]$InactiveMailboxOnly,
    [switch]$IncludeInactiveMailbox,
    [switch]$ExcludeResources
)

Process {
    try {
        if ($InactiveMailboxOnly) {
            $boxes = Get-Mailbox -InactiveMailboxOnly -SortBy DisplayName -ErrorAction Stop
        }
        elseif ($IncludeInactiveMailbox) {
            $boxes = Get-Mailbox -IncludeInactiveMailbox -SortBy DisplayName -ErrorAction Stop
        }
        else {
            $boxes = Get-Mailbox -SortBy DisplayName -ErrorAction Stop
        }

        $boxes = $boxes | Select-Object ArchiveStatus, UserPrincipalName, DisplayName, WindowsEmailAddress, IsInactiveMailbox, IsResource

        if ($ExcludeResources) {
            $boxes = $boxes | Where-Object -Property IsResource -EQ $false
        }

        if ($null -eq $boxes -or $boxes.Count -eq 0) {
            Write-Output "No mailboxes found"
            return
        }

        foreach ($box in $boxes) {
            $box | Add-Member -NotePropertyName Timestamp -NotePropertyValue (Get-Date -Format "yyyy-MM-dd HH:mm:ss") -PassThru -Force
        }
    }
    catch { throw }
}

Customize

InactiveMailboxOnly switch

Off

Include only inactive mailboxes

IncludeInactiveMailbox switch

Off

Include inactive mailboxes in results

ExcludeResources switch

Off

Exclude resource mailboxes