Can you try:

Get-MailboxStatistics | Sort-Object TotalItemSize -Descending | ft DisplayName,@{label="TotalItemSize(MB)";expression={$_.TotalItemSize.Value.ToMB()}}, Alias, PrimarySmtpAddress

Get-Mailbox | Get-MailboxStatistics | Sort totalitemsize -desc | ft displayname, totalitemsize, itemcount

get-mailbox | get-mailboxstatistics | select-object displayname, itemcount,  lastloggedonuser, lastlogontime, lastlogofftime, servername, databasename, @{ expression={$_.TotalItemSize.Value.ToKB()} }

- Rancy

Full command to csv:

Get-MailboxStatistics | Sort-Object TotalItemSize -Descending | ft DisplayName,@{label="TotalItemSize(MB)";expression={$_.TotalItemSize.Value.ToMB()}}, Alias, PrimarySmtpAddress|export-csv C:\stats.csv

@richlionel - One of my problems with Experts Exchange is when you put time and effort into helping someone who is asking a question and they don't even acknowledge it or anything. Please don't do this.

3 of us have tried to help you, please either mark one or more of the answers as the right ones sharing the points out, or instead let us know if you need more help.

chrismerritt: I agree totally with you :)
richlionel: As said it very Important you share your feedback so that if something isnt working we can try to tweek and assist you :)

- Rancy

I apologise, I was ill for a few days.

I really appreciate the help from everyone in answering! I marked ChrisMerrit's answer as the correct one since that is the one I used and it did exactly what I wanted quite well.  I hope that is the right way to do things (I'm quite new to EE).

But, everyone, thanks again! I appreciate EVERYONE's input.