Powershell Pipeline Argument not gettings passed to Set-ADUser - powershell

Question

I've been banging my head against the wall for the past few hours, I'm sure it's because I don't quite understand something about how #{} and $_ work.
First the code:
Get-ADUser username -Properties mail | Set-ADUser -replace #{"proxyaddresses"="SMTP:"+$_.mail}
As you can see I'm trying to update the proxyaddresses fields with the user's email address.
Instead only the string is pulled:(output: proxyaddresses : {SMTP:}) and the pipeline is ignored, I'm assuming it's because it's empty for some reason, but it's not clear to me why.
I've tried variations such as "proxyaddresses="SMTP:$($_.mail)" I tried using default properties that are always sent with Get-ADUser such as UserPrincipalName
I know that something like this is possible because of this http://www.itprotoday.com/management-mobility/more-flexible-active-directory-one-liner and mutiple answers on SO using some variation of the linked example.
When I assign a variable to SMTP:$_.mail and then use that in the field instead like so:
Get-ADUser username -Properties mail | %{ $smtp = "SMTP:"+$_.mail
$_|Set-ADUser -replace #{"proxyAddresses"=$smtp}
This works (output: proxyaddresses :{SMTP:emailaddress#domain.com}). If I leave out the string like so: #{"proxyaddresses"=$_.mail}
I get the following error:
Set-ADUser : Cannot bind parameter 'Replace' to the target. Exception setting "Replace": "Object reference not set to an instance of an object."
At line:1 char:58
I'm not sure what this means.
I'd like some variation of my initial idea to work, but I'll settle for the workaround using an extra variable if there's no other way.
EDIT: There seems to be some confusion about what I'm asking, so I'll clarify:
Is there a way to use the pipeline variable $_ without a script block inside a hashtable, (inside a script block requires double piping like #TheIncorrigible1 suggested in his first answer.)?
EDIT: Based on this it seems this should not be having any issues.

Answer 1

You need to use ForEach-Object to access the pipeline in the way you're trying, otherwise it doesn't know what your pipeline object ($_) is:
Get-ADUser -Identity username -Properties mail |
ForEach-Object {
$_ | Set-ADUser -Replace #{ 'proxyaddresses' = 'SMTP:' + $_.mail }
}
Or the -PipelineVariable common parameter which explicitly assigns $_ to a variable:
Get-ADUser -Identity username -Properties mail -PipelineVariable user |
Set-ADUser -Replace #{ ProxyAddresses = "SMTP:$($user.mail)" }

Answer 2

ProxyAddresses is an array where the Primary Email address is set like SMTP:primary#example.com but there can and will be other elements there too like alias email addresses (that have the lowercase smtp: prefix), SIP: addresses etc.
NEVER try to simply overwrite whatever is already there by a single string found in the mail attribute of the user object, but merge them with the ones you want to add. Selectively replace the ones you want to be changed and build an array of valid addresses.
Basically you do
$oldErrorAction = $ErrorActionPreference
$ErrorActionPreference = 'Stop'
$user = Get-AdUser -Identity $SAMAccountName -Properties mail
$primaryEmailAddress = $user.mail
$externalAddress = "smtp:<WHATEVER ALIAS YOU WOULD LIKE FOR THE USER">
$mailProxies = #("SMTP:$primaryEmailAddress", "smtp:$externalAddress")
# add more to this array if need be
$newProxies = #{'ProxyAddresses' = $mailProxies}
try {
$user | Set-ADUser -Clear ProxyAddresses
$user | Set-ADUser -Add $newProxies
}
catch {
Write-Warning "Could not set ProxyAddresses: $($_.Exception.Message)"
}
$ErrorActionPreference = $oldErrorAction

Answer 3

You may want to try set the variable first and then call on it in the script.
something like this,
$user = Get-ADUser username -Properties mail | select-object mail
Then write your script and call on the variable you may need to use foreach with a if statement to get it to function the way you want.