Table of Contents
Send from Alias Sets Record for Longest Preview Period
In January 2022, Microsoft announced the preview of the send from alias feature for Exchange Online. After much rumbling, Microsoft announced on October 7, 2026, that the feature is now generally available. I suspect most people had forgotten that send from alias was still in preview. I certainly had because so much has changed in Microsoft 365 since the feature first appeared.
In a nutshell, send from alias allows mailbox owners to use any proxy SMTP address configured for their mailbox as the message sender. When put like that, the feature sounds very straightforward and uncomplicated. So much so that you’d be forgiven for wondering why it all took so long. But the Exchange Online transport beast is a complex high-performing beast which must deal with cloud-only and hybrid environments, and any change made in that area simply must be bulletproof. I expect that’s where the root of the delay lies. Either that or blessed serendipity.
Enabling Send from Alias
Enabling the send from alias feature is simple and can be done using PowerShell by running the Set-OrganizationConfig cmdlet from the Exchange Online management module:
Set-OrganizationConfig -SendFromAliasEnabled $True
Alternatively, update the setting through the Exchange admin center (Figure 1).
Once enabled, users can send from any alias created for their mailbox. An Exchange Online tenant might have many accepted domains, all of which can support alias addresses. To prevent sending from a specific domain, configure it to disable sending with the Set-AcceptedDomain cmdlet:
Set-AcceptedDomain -Identity office365itpros.onmicrosoft.com -SendingFromDomainDisabled $True
To check what domains are enabled for sending, run:
Get-AcceptedDomain | Format-Table DomainName, SendingFromDomainDisabled
The Use Case for Send from Alias
The reason why the send from alias feature exists is to allow users greater flexibility about which SMTP address they use when sending email. This allows users to send email with different purposes, distinguished by the different addresses. In the past, the workaround was to create a shared mailbox with the desired proxy address and grant the user the SendAs permission for the shared mailbox. This approach works, but messages are channeled through the shared mailbox rather than the user’s mailbox. Using send from alias keeps sent and received messages associated with the user’s mailbox instead of routing correspondence through a separate shared mailbox.
For example, my mailbox has a proxy address called Director.IT@office365itpros.com. Let’s pretend that the intention is that messages sent from this address should convey information about IT matters. Figure 2 shows an example of a message sent using an alias.
You can clearly see the SMTP proxy address used for the message. The display name for the mailbox is shared by all proxy addresses, so the normal display name for my mailbox is shown. Some email clients show both the display name and proxy address. Others, including Outlook, attempt to resolve the SMTP address against the directory and display the mailbox name instead.
Other email clients simply show the SMTP address, which is when send from alias works best (Figure 4).
Some Gaps to Close
As you’d expect, the set of known issues is less than when the feature first appeared in preview. However, Microsoft still has a few gaps to close before messages sent using aliases support every capability available when sending from a primary SMTP address. The remaining limitations are much smaller than they once were, but administrators should review the known issues before enabling the feature broadly.
Microsoft 365 for IT Pros is a trusted source of technical insight that helps tenant administrators stay informed and productive. We update the content every month to reflect changes across Microsoft 365, and monthly update #136 is available now. Get your copy from Gumroad.com and stay up to date with the information that matters most for keeping your tenant secure, compliant, and running efficiently.