How to get a list of email aliases from Microsoft 365

Problem:

You want to obtain a list of all email aliases configured in your Microsoft 365 organization. 

Solution:

While you can check this information manually in the Microsoft 365 admin center, doing so requires navigating to user profile cards one by one, which is not time-efficient. The easiest way to get a list of aliases in your Microsoft 365 tenant is by using PowerShell (see this article to learn more about connecting to your organization with PowerShell).

The script below returns a list of mailboxes with aliases configured. Check the comments in the script for more information.

Connect-ExchangeOnline # First, you need to connect Exchange Online with PowerShell. You’ll need to sign in with a Microsoft 365 admin account.

$mailboxes = (Get-Mailbox | select-object displayname, primarysmtpaddress, emailaddresses) # Gets relevant parameters of all mailboxes in your Microsoft 365 tenant. You can use -Filter to limit the number of processed mailboxes.

$AllAliases = @() # An array that will store users addresses and aliases.

foreach ($mailbox in $mailboxes){ #This script goes through the list of your mailboxes.

foreach ($address in $mailbox.EmailAddresses){

if ($address -match "smtp:"){ # Filters only SMTP addresses, leaves out, for example, SPO addresses.

$alias = New-Object PSObject # A new object that lists display names, primary SMTP address and aliases of mailboxes in your tenant.

$alias | add-member -type NoteProperty -name 'DisplayName' -Value $mailbox.DisplayName

$alias | add-member -type NoteProperty -name 'PrimarySmtpAddress' -Value $mailbox.PrimarySmtpAddress

$alias | add-member -type NoteProperty -name 'EmailAddress' -Value $address.Split(':')[1] # Gets only the email address, without its SMTP label.

if($alias.EmailAddress -ne $alias.PrimarySMTPAddress){ # Filters results so that only aliases are added to the $AllAliases array.

$AllAliases += $alias

}

}

}

}

$AllAliases # Shows the list of all mailboxes that have aliases configured. You can group results by adding | Group-Object DisplayName

Once you run the script, you'll get results similar to those shown in Fig. 1. Aliases are listed in the EmailAddress column.

Fig. 1. Example of obtaining a list of aliases by using PowerShell.

You can use the follow-up script below to list all aliases, separated by semicolons (as shown in Fig. 2.):

$AllAliases | foreach{

Write-Host $_.EmailAddress "; " -NoNewLine

}

Fig. 2. All email aliases listed and separated by semicolons.

You can copy the results to your clipboard and paste them directly into CodeTwo Email Signatures 365 (Fig. 3.). For step-by-step instructions on how to set up different signatures for emails sent from alias addresses, see this article.

Fig. 3. Creating a signature rule for email aliases in CodeTwo.