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Adding New Email Addresses for Multiple Mailbox Users

Email addresses are an ever changing requirement for many organizations, particularly when mergers, acquisitions, or re-branding exercises are under way. Naturally this is something that falls on the Exchange administrator to solve. There’s a variety of scenarios that could be put in front of you, depending on whether it is all or just some of the users in the organization that require an email address change. It also varies depending on whether you’re running an on-premises Exchange Server organization, a Hybrid configuration, or are running purely in Exchange Online (Office 365).

Here’s a summary of the approaches you can use:

  • For on-premises and Hybrid organizations, bulk email address changes (whether to all users or just a subset of users) can be managed with email address policies. You can also manually modify email addresses for individual recipients, or for multiple recipients using PowerShell.
  • For cloud-only Office 365 organizations, bulk email address changes can be made when adding a new domain to your tenant, or at any time you can bulk add SMTP addresses to multiple mailboxes using PowerShell.

Let’s start at the beginning.

Adding a New Domain Name to Exchange Server or Exchange Online

Before your organization can accept email for a domain name the domain needs to be added to your config. For on-premises Exchange organizations this is managed as Accepted Domains.


There are three types of accepted domains to choose from:

  • Authoritative – your organization is the only system that has recipients with email addresses in that domain.
  • Internal Relay – your organization shares the domain name with another organization or system (also known as a shared SMTP namespace).
  • External Relay – your organization has no recipients for that domain name, but will accept and route email for that domain to another destination.

For an Exchange Online (Office 365) tenant, a custom domain needs to be added. To prevent you from adding domains that you do not own or control, you’ll be required to verify the custom domain name by adding a specific DNS record to your public DNS zone. Note also that a custom domain can’t be added to more than one Office 365 tenant at the same time.


For Hybrid deployments the domain should be added to both the on-premises organization, and to the Office 365 tenant.

Adding Email Addresses to Recipients

After the domain has been added to your organization and/or tenant, you can begin adding email addresses to your recipients.

Adding Email Addresses to Multiple Recipients using Email Address Policies

For on-premises and Hybrid deployments you can use email address policies to achieve this. Every on-premises organization has at least one email address policy that is the default, and you can add more policies as needed. There are two parts to the policy. The first is the address format. You can choose from pre-canned formats such as “alias@domain.com”, or construct your own using variables. Note that you can’t use a domain name in a policy until it has been added to the organization as an accepted domain.


The second part is the filters or rules that control which recipients the email address policy will apply to. The default policy applies to all recipients, but you can be more granular for your additional policies as necessary to meet your needs.


Notice the sequence number as well? That allows you to control which policies take precedence over others. A recipient has a single policy applied to them at any time, so if there are multiple policies that match a recipient, it will be the highest priority match that is applied. The highest priority policy is the number 1, and the default policy is always the lowest priority.


Note that for Hybrid deployments you should first add the domain to both the on-premises organization and to the Office 365 tenant before you begin applying new email address policies.

Adding Email Addresses to Multiple Recipients when Adding a Custom Domain to Office 365

For Office 365 customers you can choose to add a new email address to multiple recipients during the process of adding a custom domain to the tenant.


Adding Email Addresses to Recipients Using PowerShell

For on-premises and Hybrid deployments we can use PowerShell to manage email addresses. For a recipient that is enabled for email address policies, we can use PowerShell to manage any additional (secondary) email addresses. If we want to manage the primary email address for the user, then they’ll need to be disabled for email address policies.

For more on this read the following article:

For Office 365 tenants there are no email address policies. Therefore all management of both primary and secondary email addresses can be performed using PowerShell. The same techniques shown in the link above can be used, or we can use a script to perform bulk changes.

Note that the script makes changes to all mailboxes in the tenant, unless you follow the steps to modify the $mailboxes that it applies to. Please read, understand, and test the script before making changes to production users.


In this article I’ve covered the various methods that can be used to add new email address to multiple users. You’ve seen that there are multiple techniques that can be used, depending on whether you are managing an on-premises, Hybrid, or cloud-only organization, and also depending on how many recipients you want to modify.

Paul is a Microsoft MVP for Office Servers and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul is a co-author of Office 365 for IT Pros and several other books, and is also a Pluralsight author.
Category: Exchange Server


  1. James says:

    Paul, I’m not clear if I will be able to reply using the different email addresses, ie depending on which email the mail was sent to could I reply with different email addresses?

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