How to add email address based on email alias? Get-Mailbox | Set-Mailbox -EmailAddresses @{add= $_.Alias + "@TEST"}

Question

I can't get this to work via the pipeline, but if I type in someones specific email address to get, it works fine.  Any help on the syntax?
Thanks!
Get-Mailbox [email protected] | Set-Mailbox -EmailAddresses @{add= $_.Alias + "@TEST"}                                        
: NOT WORKING.  This just adds "@TEST" to the email addresses
$test = Get-Mailbox [email protected]
Get-Mailbox [email protected] | Set-Mailbox -EmailAddresses @{add= $test.Alias + "@TEST"}            : WORKING.  This adds "me@TEST" to the email addresses

Answer 1

Wow, lots to try!  Thanks for the help.
Can you help me understand what this is doing?
@{Add="$($_.Alias)@TEST"}
I understand $_ is the current object in the pipeline, but how do I interpret the $($_.Alias)?
Sure, the extra $() surrounding $_.Alias is known as the subexpression operator:
http://ss64.com/ps/syntax-operators.html
Basically this allows you to use a property directly inside of a string. It's important to use double quotes in this instance, so the string can expand.
EDIT: Here's an example you can run with Get-Mailbox:
Get-Mailbox |
ForEach { Write-Host "This will append @TEST to the username: $($_.SamAccountName)@TEST" }
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