Forward All Emails from a Mailbox to a Distribution Group

Configure forwarding via the Exchange Admin Center

The Exchange Admin Center (EAC) is the most reliable GUI path because it writes to the same mailbox properties as Set-Mailbox.

Step 1 — Open the Exchange Admin Center

1. Sign in to https://admin.exchange.microsoft.com as an Exchange Administrator
2. Navigate to Recipients → Mailboxes

Step 2 — Locate the source mailbox

1. Search for the mailbox by display name or primary SMTP (e.g. {source_mailbox})
2. Click the mailbox to open its properties pane
3. Confirm the aliases listed under Email addresses match what you expect (e.g. {primary_address} and {alias_address}) — all aliases automatically inherit the forwarding setting

Step 3 — Configure mail flow forwarding

1. Select the Mailbox tab in the properties pane
2. Under Mail flow settings, click Manage email forwarding
3. Toggle Forward all emails sent to this mailbox to On
4. In Forwarding address, enter the distribution group's primary SMTP address (e.g. {target_group}@{domain})
5. Check Deliver message to both forwarding address and mailbox if you want to retain a copy in the source mailbox (recommended for audit)
6. Click Save

Step 4 — Validate

1. From an external account, send a test message to the primary address ({primary_address})
2. Send a second test message to each alias ({alias_address})
3. Confirm that members of {target_group} receive both messages
4. If you enabled Deliver to both, confirm the source mailbox also retains copies

Graph API approach (limitations apply)

Important: Microsoft Graph does not expose the canonical ForwardingAddress / ForwardingSmtpAddress mailbox properties. The only forwarding mechanism available via Graph is an Inbox rule, which is weaker than mailbox-level forwarding (it can be deleted by the user and only processes messages that land in the Inbox folder). For production-grade forwarding, use the PowerShell recipe below.

Step 1 — Look up the source mailbox

GET https://graph.microsoft.com/v1.0/users/{source_mailbox}?$select=id,displayName,userPrincipalName,proxyAddresses

Response includes the mailbox id and all SMTP aliases in proxyAddresses (aliases prefixed smtp:, primary prefixed SMTP:).

Step 2 — Look up the target distribution group

GET https://graph.microsoft.com/v1.0/groups?$filter=mail eq '{target_group}@{domain}'&$select=id,displayName,mail,mailEnabled

Confirm mailEnabled is true — a security-only group cannot receive forwarded mail.

Step 3 — Create an inbox rule on the source mailbox

POST https://graph.microsoft.com/v1.0/users/{mailbox_id}/mailFolders/inbox/messageRules
Content-Type: application/json

{
  "displayName": "Forward all to {target_group}",
  "sequence": 1,
  "isEnabled": true,
  "conditions": {},
  "actions": {
    "forwardTo": [
      {
        "emailAddress": {
          "address": "{target_group}@{domain}"
        }
      }
    ],
    "stopProcessingRules": true
  }
}

An empty conditions object means the rule matches every incoming message. Response 201 Created returns the rule id.

Gotchas

• The signed-in context needs Mail.ReadWrite and often Mail.ReadWrite.Shared for shared mailboxes; admin consent alone is not always sufficient — the admin may also need explicit Full Access permission on the target mailbox in Exchange.
• Inbox rules do not apply to mail delivered to the Junk Email folder or to messages routed by transport rules before they hit the Inbox.
• For a durable, tenant-enforced setup, prefer the PowerShell path.

Configure forwarding via Exchange Online PowerShell (recommended)

This is the canonical, supported way to configure mailbox forwarding and what the Exchange Admin Center calls under the hood.

Step 1 — Connect to Exchange Online

# Install module once, if needed
Install-Module -Name ExchangeOnlineManagement -Scope CurrentUser

# Connect as an Exchange Administrator
Connect-ExchangeOnline -UserPrincipalName admin@{domain}

Step 2 — Verify the source mailbox and target group

Get-Mailbox -Identity "{source_mailbox}" | Select-Object DisplayName,PrimarySmtpAddress,EmailAddresses,RecipientTypeDetails

Get-DistributionGroup -Identity "{target_group}@{domain}" | Select-Object DisplayName,PrimarySmtpAddress,MemberJoinRestriction

Step 3 — Apply forwarding

# Forward and keep a copy in the source mailbox
Set-Mailbox -Identity "{source_mailbox}" `
    -ForwardingAddress "{target_group}@{domain}" `
    -DeliverToMailboxAndForward $true

ForwardingAddress expects a recipient that exists in the directory (like a distribution group) and is the preferred property. Use ForwardingSmtpAddress only for external/non-directory addresses.

Step 4 — Confirm

Get-Mailbox -Identity "{source_mailbox}" | Select-Object PrimarySmtpAddress,ForwardingAddress,ForwardingSmtpAddress,DeliverToMailboxAndForward

Step 5 — Test and monitor

1. Send test messages to both the primary address and each alias
2. Check message trace: Get-MessageTrace -RecipientAddress {source_mailbox} -StartDate (Get-Date).AddHours(-1) -EndDate (Get-Date)

To remove forwarding later

Set-Mailbox -Identity "{source_mailbox}" -ForwardingAddress $null -ForwardingSmtpAddress $null