PowerShell Commands to Extract External User Email Addresses

Question

There is a need to retrieve email address information of external users for supporting an email campaign. Looking for PowerShell commands that can extract all email addresses from the mailbox, specifically targeting external users outside the organization.

Additionally, the goal is to perform this action for all users in the organization simultaneously.

Note: Emails from the past 4-5 years are visible in the Outlook account, but verifying every email manually is a big process. Any assistance or possibilities to retrieve this data would be appreciated.

Answer 1

Hello, @Mohana Reddy,

Welcome to the Microsoft Q&A platform!

Here's a general approach to extract email addresses of external users from mailboxes:

1.Connect to Exchange Online: First, ensure you have the Exchange Online PowerShell module installed. Then, connect to Exchange Online:

Connect-ExchangeOnline -UserPrincipalName ******@domain.com -ShowProgress $true

2.Retrieve External Email Addresses: You can use the following script to extract email addresses from all mailboxes. This script filters out internal email addresses based on your domain:

$domain = "yourdomain.com"
$externalEmails = @()

$mailboxes = Get-Mailbox -ResultSize Unlimited
foreach ($mailbox in $mailboxes) {
    $emails = Get-MailboxFolderStatistics -Identity $mailbox.UserPrincipalName | Where-Object {$_.FolderType -eq "Inbox"} | ForEach-Object {
        Get-Content -Path $_.FolderPath
    }
    foreach ($email in $emails) {
        if ($email.SenderEmailAddress -notlike "*@$domain") {
            $externalEmails += $email.SenderEmailAddress
        }
    }
}

$externalEmails | Sort-Object -Unique | Out-File "ExternalEmailAddresses.txt"

(Please Note: Replace "yourdomain.com" with your actual domain. This script assumes that external email addresses do not contain your domain name and saves the unique external email addresses to a file named ExternalEmailAddresses.txt.)

Should you need more help on this, you can feel free to post back. 

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Thank you for your support and understanding.

Best Wishes,

Alex Zhang