If you are using Exchange Archive Online, sometimes you need to identify mailboxes with enabled Archive.
To get list of Archive enabled mailboxes you can use EMS console and following command:
Get-Mailbox -ResultSize Unlimited | where {$_.ArchiveDatabase -ne $Null}
As a result you will get list of all mailboxes with Archive Online enabled, but you won’t get information about database where this archive is stored.
To get list of all mailboxes with information where are they in databases you can use following command:
Get-Mailbox -ResultSize Unlimited | where {$_.ArchiveDatabase -ne $Null} | Select Name, ArchiveDatabase, ArchiveName
English 
polski