Email Forwarding in Exchange and Microsoft 365: ForwardingSmtpAddress vs. ForwardingAddress

Email forwarding is an essential feature in Exchange and Microsoft 365, but many find it tricky to differentiate between two key parameters: ForwardingSmtpAddress and ForwardingAddress. Let’s dive into these concepts and understand how they work.

1??ForwardingSmtpAddress: For External Recipients

The ForwardingSmtpAddress parameter is used when you want to forward emails to external recipients outside your organization. These addresses don’t require validation as internal recipients, making it ideal for scenarios where users need emails redirected to personal accounts like Gmail or Yahoo.

?? Example: Your organization has a contractor, Jane, who prefers receiving emails at her personal address, [email protected]. By setting her mailbox’s ForwardingSmtpAddress to this Gmail address, all her emails are automatically sent there.

2??ForwardingAddress: For Internal Recipients

The ForwardingAddress parameter is designed for forwarding emails to internal recipients within your organization. These recipients are validated and can be specified using various identifiers like alias, distinguished name, or GUID.

?? Example: Mark is leaving the company, but his manager, Sarah, still needs to monitor his incoming emails. You can set Mark’s mailbox ForwardingAddress to Sarah’s internal account (e.g., [email protected]).

DeliverToMailboxAndForward: Controlling Delivery Behavior

The DeliverToMailboxAndForward parameter decides whether emails are:

1?? Delivered to the original mailbox and forwarded (set to $true).

2?? Only forwarded to the recipient, skipping the original mailbox (set to $false).

?? Example: Mark’s mailbox is set to forward emails to Sarah. If DeliverToMailboxAndForward is $true, emails will remain in Mark’s inbox and be forwarded to Sarah. If it’s $false, emails will only be forwarded to Sarah, and Mark won’t receive them in his mailbox.

Key Behavior: Precedence of ForwardingAddress

When both ForwardingSmtpAddress and ForwardingAddress are configured, the system prioritizes ForwardingAddress. This means internal forwarding takes precedence over external forwarding.

?? Scenario Example: You configure both Jane’s external Gmail address (via ForwardingSmtpAddress) and Sarah’s internal address (via ForwardingAddress). Emails sent to Jane’s mailbox will only forward to Sarah, ignoring the Gmail address.

How to Configure Email Forwarding

1?? Using Outlook on the Web (OWA):

• Navigate to Settings > Mail > Forwarding.
• Configure ForwardingSmtpAddress here.

2?? Using Exchange Admin Center (EAC):

• Go to the mailbox properties and open the Email Forwarding tab.
• Use ForwardingAddress for internal recipients or ForwardingSmtpAddress for external recipients.

3?? Using Microsoft 365 Admin Center:

• Email forwarding here automatically sets ForwardingSmtpAddress.

Why Understanding These Parameters Matters

Understanding these settings can save you a lot of time, whether you’re troubleshooting or setting up seamless email forwarding. Here are some insights:

1. Transport Rules and ForwardingSMTPAddress: When an admin sets a forwarding address using the Exchange Admin Center (EAC) with ForwardingSMTPAddress, certain transport rules may not work as expected. For example, if a rule is set to reject messages based on the X-MS-Exchange-ForwardingLoop header, it might not work because this header is added after the message is evaluated by transport rules.
2. Mail Forwarding in Tenant Migration: During a tenant-to-tenant migration, you can enable mail forwarding on the "old" mailbox to send a copy of incoming messages to the "new" mailbox using the Set-Mailbox command with the ForwardingSMTPAddress parameter. This ensures that incoming emails are delivered to both mailboxes during the migration process.
3. Remote Domains and AutoForwardEnabled Setting: The ForwardingSMTPAddress is subject to the Remote Domain's AutoForwardEnabled setting. This means that if auto-forwarding is disabled for a remote domain, the ForwardingSMTPAddress will also be affected.

Have you faced challenges with email forwarding in your organization? Let’s discuss your experiences below!