Kevin Mychal Ong I was only thinking of maryh2020 when I mentioned about the -ExchangeGuid parameter.
I just tested with Get-EXOMailbox | Get-EXOMailboxStatistics and it works for me, I'm using the latest version - 0.4578.0.
On the Get-EXOMailboxStatistics docs page, it shows "True (ByPropertyName)" for pipeline input for -Identity, -DatabaseGuid, -ExchangeGuid, and -UserPrincipalName, so any objects being piped in that have any of these properties on them (and with valid values of course) should work. However, check this out:
>$ExchGuids = Get-EXOMailbox -Properties ExchangeGuid | select ExchangeGuid
>$ExchGuids | Get-EXOMailboxStatistics
Notice how I've made sure to get the ExchangeGuid property in my output from Get-EXOMailbox (using -Properties ExchangeGuid)? That is a must in order to successfully execute the second command, because ExchangeGuid isn't a default property in the output of Get-EXOMailbox.
In case it's of any help, feel free to look at my script Get-EXOMailboxTrustee.ps1 (https://github.com/JeremyTBradshaw/PowerShell/blob/master/Get-EXOMailboxTrustee.ps1). I am not piping into any of the new cmdlets in that script but I'm using Get-EXOMailbox, Get-EXOMailboxPermission, Get-EXOMailboxFolderPermission, and Get-EXORecipientPermission. Since all the new cmdlets are going to be changing for a while it's likely that script will change too. But anyway, just wanted to share that.
So we have working pipeline for several properties and we can also go no-pipe and use the same properties manually instead, and in a foreach loop if needed.