Check Archive Mailbox Size

Single Mailbox

Archive Used

Get-MailboxStatistics (Read Host "Enter Email") -Archive | Select DisplayName, TotalItemSize, ItemCount

Archive Max

Get-Mailbox -Identity (Read-Host "Enter Email") | Select ArchiveQuota, ArchiveWarningQuota, AutoExpandingArchiveEnabled

All Archive Mailboxes

Get-Mailbox -ResultSize Unlimited | Get-MailboxStatistics -Archive | Select DisplayName, TotalItemSize | Sort TotalItemSize -Descending

Very Related to AutoExpandingArchive

Notes

• The -Archive switch is required — without it, the command returns primary mailbox stats instead of the archive.
• Must be connected to Exchange Online PowerShell first: Connect-ExchangeOnline