Each Exchange mailbox can be assigned multiple email addresses. These proxy addresses are also called aliases. Until now, you could use them to receive messages, but to send emails, you had to use the standard address. Now Microsoft 365 also allows you to send email via an alias.

Previously, if you wanted to send an email from an alias address, workarounds such as using a shared mailbox or distribution group were necessary.

Sending messages on behalf of an alias is on Microsoft’s roadmap, and it is currently being introduced in Exchange Online. This option is available in both the Outlook desktop client and the web app.

Changing the tenant configuration ^

To enable sending email from an alias address, you first need to modify the organization’s configuration at the tenant level. The following PowerShell command serves this purpose:

Set-OrganizationConfig -SendFromAliasEnabled $true

Use the following cmdlet to ensure your configuration is successful:

Get-OrganizationConfig | Select-Object SendFromAliasEnabled

Managing alias addresses ^

Alias addresses can be maintained via several administration options. If you prefer a graphical interface, you can find it in the Microsoft 365 Admin Center or the Exchange Admin Center.

There, follow the link Manage username and email in the account properties. On the following page, you can add aliases using the corresponding field.

In PowerShell, the Set-Mailbox cmdlet is used to manage aliases (the respective parameter is named EmailAdresses). The following command adds additional SMTP addresses:

Set-Mailbox -Identity [Identity] -EmailAddresses @{add=”[alias-address]”}

Sending from the alias address ^

In my test environment, sending from the additional SMTP address was possible after a few minutes. It might take a bit longer if the change hasn’t taken effect yet. For testing, I used a current Outlook version.

There, you first have to open the “From” field and then select Other Email Address. In the dialog box that appears, you can enter the desired sender address.

To the recipient, the mail looks as if the alias were the primary SMTP address (as shown in the following figure).

The alias also appears in the email header as the From address.