How to: Add Multiple Email Addresses to Distribution Groups in Microsoft 365

Introduction

Microsoft 365 distribution groups provide an efficient way to send emails to multiple recipients using a single email address. However, there are situations where a distribution group needs multiple email addresses (also known as proxy addresses or aliases) – perhaps to maintain backward compatibility with legacy email addresses, support different domains, or create easy-to-remember aliases for different departments.

While the Microsoft 365 admin center allows you to create and manage distribution groups, it doesn’t provide a way to add multiple email addresses to a distribution group through the web interface. This functionality requires using PowerShell, which gives administrators more control and automation capabilities.

The Problem

The Microsoft 365 admin center doesn’t provide an option to add multiple SMTP proxy addresses to cloud-only distribution groups. When organizations need to:

• Maintain legacy email addresses after a migration
• Support email delivery to distribution groups across multiple domains
• Create intuitive aliases for specialized functions
• Implement email standardization while maintaining backward compatibility

Adding these additional email addresses requires PowerShell commands, as this functionality isn’t available in the standard web interface.

Solution Options

Option 1: Using Exchange Online PowerShell V3 Module (Recommended Method)

The Exchange Online PowerShell V3 module is the current recommended method for managing Exchange Online, including distribution groups. This module uses modern authentication and REST API, making it more secure and reliable than older connection methods.

Step 1: Install the Exchange Online PowerShell V3 Module

# Install the Exchange Online PowerShell V3 module
Install-Module -Name ExchangeOnlineManagement -Force

Step 2: Connect to Exchange Online

# Connect to Exchange Online with your admin account
Connect-ExchangeOnline -UserPrincipalName admin@yourdomain.com

Step 3: Add Email Addresses to the Distribution Group

# Add multiple email addresses to a distribution group
Set-DistributionGroup "Group Name" -EmailAddresses @{Add="secondary.email@domain.com","another.email@domain.com"}

Step 4: Verify the Changes

# Verify that the email addresses were added
Get-DistributionGroup "Group Name" | Select-Object -ExpandProperty EmailAddresses

Step 5: Disconnect from Exchange Online

# Disconnect when finished
Disconnect-ExchangeOnline -Confirm:$false

Option 2: Bulk Operations Using CSV Files

For managing multiple distribution groups or adding multiple email addresses at scale, you can use a CSV file approach.

Step 1: Create a CSV File

Create a CSV file with the following structure:

PrimarySmtpAddress,SecondaryEmail
group@domain.com,secondary1@domain.com
group@domain.com,secondary2@domain.com
anothergroup@domain.com,another1@domain.com

Step 2: Run the PowerShell Script

# Connect to Exchange Online
Connect-ExchangeOnline -UserPrincipalName admin@yourdomain.com

# Import the CSV and process each line
$groups = Import-Csv -Path "C:\Path\To\Your\File.csv"
foreach ($item in $groups) {
    Set-DistributionGroup -Identity $item.PrimarySmtpAddress -EmailAddresses @{Add=$item.SecondaryEmail}
    Write-Host "Added $($item.SecondaryEmail) to $($item.PrimarySmtpAddress)" -ForegroundColor Green
}

# Disconnect when finished
Disconnect-ExchangeOnline -Confirm:$false

Automating Management

To further automate the management of distribution group email addresses, you can:

1. Create Scheduled Tasks: Use Windows Task Scheduler to run scripts periodically for maintaining distribution groups.
2. Implement Error Handling:

try {
    Set-DistributionGroup "Group Name" -EmailAddresses @{Add="secondary.email@domain.com"}
    Write-Host "Email address added successfully" -ForegroundColor Green
} catch {
    Write-Host "Error adding email address: $_" -ForegroundColor Red
    # Send notification or log error
}

3. Integrate with Change Management: Create approval workflows that automatically run scripts when approved through your organization’s change management system.
4. Create Self-Service Portals: Develop web interfaces that call PowerShell scripts, allowing authorized users to request new email addresses for distribution groups without direct PowerShell access.

Conclusion

While Microsoft 365’s web interface doesn’t provide a way to add multiple email addresses to distribution groups, PowerShell offers a powerful and flexible solution. The Exchange Online PowerShell V3 module with modern authentication provides a secure and efficient way to manage distribution group email addresses, whether for individual groups or bulk operations.

By leveraging PowerShell scripts, you can automate the process, integrate it with your existing workflows, and ensure consistent distribution group management across your organization. This approach offers greater control and efficiency compared to manual administration through the web interface.

Need Help?

Contact me for assistance with setting up automated distribution group management, custom PowerShell scripts, or other Microsoft 365 administration tasks. I can help design solutions that fit your specific organizational needs and governance requirements.

References

1. Microsoft Learn – Create and manage distribution groups in Exchange Online
2. Microsoft Learn – Connect to Exchange Online PowerShell
3. Microsoft Learn – Set-DistributionGroup cmdlet reference
4. Microsoft Learn – Add-DistributionGroupMember
5. Microsoft 365 admin center – Create distribution lists