Add ProxyAddresses to separate script - powershell

Question

Goal: Append script to add three different SMTP addresses.
Script: https://thesysadminchannel.com/how-to-create-o365-mailboxes-hybrid-exchange/
Code Snippet:
Write-Host "Continuing will create the AD account and O365 Email." -ForegroundColor:Green
Write-Host
$Proceed = $null
$Proceed = Read-Host "Continue? (y/n)"
if ($Proceed -ieq 'y') {
Write-Host "Creating the O365 mailbox and AD Account."
New-RemoteMailbox -Name $fullname -FirstName $firstname -LastName $lastname -DisplayName
$fullname -SamAccountName $logonname -UserPrincipalName $logonname#$domain -PrimarySmtpAddress
$logonname#$domain -Password $password -OnPremisesOrganizationalUnit $OU -DomainController $Server
Write-Host "Done..."
Write-Host
Write-Host
Sleep 5
Write-Host "Adding Properties to the new user account."
Get-ADUser $logonname -Server $Server | Set-ADUser -Server $Server -Description $Description -
Office $Office -StreetAddress $StreetAddress -City $City -State $State -PostalCode $PostalCode -
Country $Country -Title $Title -Department $Department -Company $Company -Manager $Manager -
EmployeeID
$EmployeeID
Write-Host "Done..."
Write-Host
Write-Host
if ($MemberOf) {
Write-Host "Adding Membership Groups to the new user account."
Get-ADUser $logonname -Server $Server | Add-ADPrincipalGroupMembership -Server $Server -
MemberOf $MemberOf
Write-Host "Done..."
Write-Host
Write-Host
}
}
Get-PSSession | Remove-PSSession
What I'm trying to add are these three values:
SMTP:user#domain.com
smtp:user#domain.mail.onmicrosoft.com
smtp:user#domain.onmicrosoft.com
This is along the lines of what I've come up with:
Write-Host "Adding Properties to the new user account."
Get-ADUser $logonname -Server $Server | Set-ADUser -Server $Server -Description $Description
-Office $Office -StreetAddress $StreetAddress -City $City -State $State -PostalCode $PostalCode -
Country $Country -Title $Title -Department $Department -Company $Company -Manager $Manager -
EmployeeID $EmployeeID
Write-Host "Done..."
Write-Host
Write-Host
Write-Host “Setting up TCS E-mail Standard”
$userinfo.ProxyAddresses = "SMTP:" + ($FirstInitial.Add(1)) + ($userinfo.sn) +
"#DOMAIN.COM"
#$userinfo.ProxyAddresses += "smtp:" + ($userinfo.givenname) + "." + ($userinfo.sn) +
"#domain.mail.onmicrosoft.com"
$userinfo.ProxyAddresses += "smtp:" + ($FirstInitial.Remove(1)) + ($userinfo.sn) +
"#domain.onmicrosoft.com"
$userinfo.targetAddress = "SMTP:" + ($userinfo.sAMAccountName) +
"#domain.mail.onmicrosoft.com"
Write-Host "Done..."
Write-Host
Then I get this error:
You cannot call a method on a null-valued expression.
At C:\Users\Temp\CreateStudentEmail.ps1:233 char:21
+ ... $userinfo.ProxyAddresses = "SMTP:" + ($FirstInitial.Add(1 ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
You cannot call a method on a null-valued expression.
At C:\Users\Temp\CreateStudentEmail.ps1:235 char:21
+ ... $userinfo.ProxyAddresses += "smtp:" + ($FirstInitial.Rem ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
The property 'targetAddress' cannot be found on this object. Verify that the property exists and can
be set.
At C:\Users\Temp\CreateStudentEmail.ps1:236 char:21
+ ... $userinfo.targetAddress = "SMTP:" + ($userinfo.sAMAccou ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : PropertyNotFound
Just trying to find a way to incorporate the proxy address section so that I don't have to worry about extra steps.
I pulled the code from another PowerShell I used years ago, then tweaked it a bit, but it DOES actually input SMTP address fields into the AD character. It still throws errors though.

Answer 1

Here is what you need to do:
set-Aduser $samaccountname -Add #{ proxyAddresses = "SMTP:user#domain.com","smtp:user#domain.mail.onmicrosoft.com","smtp:user#domain.onmicrosoft.com" }