Powershell - get all mailboxes size from exchange server

get-mailbox -server yourexchangeservername -ResultSize unlimited | select-object Alias, IssueWarningQuota, ProhibitSendQuota, @{label="TotalItemSize(MB)";expression={(get-mailboxstatistics $_).TotalItemSize.Value.ToMB()}}, @{label="ItemCount";expression={(get-mailboxstatistics $_).ItemCount}}, Database | Export-Csv "UserMailboxSizes.csv" –NoTypeInformation