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Exchange Team Blog

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Sending From Email Aliases – Public Preview

Microsoft

Jan 25, 2022

Historically, Exchange has used a user’s primary SMTP address as the From address when sending messages. Other SMTP addresses assigned to a user (e.g., proxy addresses, also known as aliases) were mainly intended for receiving messages. Even when an email client tries to use an alias for the From address, that value is overwritten with the user’s primary SMTP address when the message is sent.

Today, business operations are much more challenging and complex, and activities such as mergers and acquisitions, rebranding, and other such changes have created the need for multiple identities and SMTP domains to be managed by an organization. To address these challenges, we started a journey toward making aliases first-class addresses in Exchange Online. We are excited to announce that we’ve reached the first milestone of this journey.
In the past, those wanting to send from aliases had a few options. They could use the SMTP AUTH client submission protocol, which didn’t rewrite the From addresses. Shared mailboxes could be used, but that meant another identity and another Inbox, as well.

To eliminate the need for these suboptimal solutions, we have introduced new capabilities in Exchange Online that enable Outlook clients to use and preserve aliases and to display the original alias used to send the message. This is accomplished by no longer replacing aliases during the sending or delivery of messages in Exchange Online.

The new capabilities are now available in Public Preview for Outlook on the Web and Outlook for iOS and Android. You can access the Preview using the SendFromAliasEnabled parameter of the Set-OrganizationConfig cmdlet. The setting enables the new functionality for all Exchange Online mailboxes in the organization. Note: it might take up to 60 minutes for this change to take effect in your tenant.

This feature is in Preview because we have made fundamental changes throughout the email pipeline. There are known compatibility issues with some features that assume the user’s primary SMTP address will always be used. These known issues are listed below. We will work to the update the known issues list in this post periodically.

This is the first iteration of our support for aliases. We do have plans for additional functionality, but we want to hear from customers about what they want.
Client support
Support for sending from aliases has been added to Outlook on the web and Outlook for iOS and Android. Mobile clients allow users to enter aliases in the From field and those will be saved for future use. Support for Outlook for Windows was enabled at Monthly Channel 100% starting 1/17/23. We will update here when the feature advances to other channels. Desktop clients will display a list of enabled aliases in the From field, and messages sent from an alias will have that address preserved.

Aliases will also be preserved when messages are addressed to them. If a user replies to a message that was sent to their alias, their reply will come from the alias by default.
Outlook on the web
The From drop-down now contains a list of available aliases:

This list of aliases can be customized by the user in Settings from the full list of aliases (proxy addresses) that are associated with their mailbox.

Outlook for iOS and Android
Aliases can be entered into the From field. Previously used aliases will be saved and available via a dropdown list:

Outlook for Windows
Support for aliases is on the way for Outlook for Windows. The From field will also support a customized list of aliases.

It’s possible to customize the list by clicking on Manage List…, which is the same as changing them on the Settings page in Outlook on the web.

Outlook for Mac support for this feature is planned (we will provide more information as it becomes available).

Known Issues
This being a preview, we are aware of several known issues (updated October 2024):

In Hybrid scenarios, when email is sent from on-premises to Exchange Online, email is sent to user’s mail.contoso.onmicrosoft.com address. With send-as-alias feature enabled, this address is preserved and not resolved to user’s primary address. This can cause issues like OOF response coming from user’s mail.contoso.onmicrosoft.com address instead of the email address representing user’s actual email domain name (contoso.com).
Outlook Desktop not being able to send from an alias in Online Mode or if an OAB is not present is fixed in Version 2403 (Build 17425.20236).
For shared mailbox, send from alias feature works only with OWA when delegate opens it using “Open another mailbox” option. For Outlook client, send from alias feature is not supported for shared mailbox at all.
Similarly to shared mailbox mentioned above, send as alias feature does not work using Outlook for regular user mailboxes with “Send As” or “Full Mailbox” permissions.
Outlook for Windows currently shows the original email address instead of the alias if an internal user replies on an email. If you intend to use aliases where you will have replies from external parties and internal parties on the same email make sure to factor in this limitation.
Various types of rules in Exchange Online, such as hygiene or journaling rules that are configured to look for specific email addresses, may not match aliases, resulting in the rule not acting on those messages.
- Multiple customers have reported issues with journaling rules not triggering messages with aliases.
- Messages sent to aliases were rewritten to the primary SMTP address in the past. Complex routing configurations may rely on this behavior. When the sending from aliases feature is enabled, rewriting to the user’s primary SMTP address will stop, which could break routing. Customers have seen this when aliases with different domains are used
- Forwarding/Redirecting using Inbox Rules sees the address being sent to resolved to the primary SMTP address while the Resent-From header shows the alias address used.
Different email addresses or display names may appear. Some companies have set up Outlook clients with aliases or display names that differ from the user’s primary email address and display name stored on the mailbox. When the sending from aliases feature is enabled, it may cause a change in behavior for what shows up in sent messages’ From field.
When using the user’s primary SMTP address in a Message Trace query, the results do not include messages sent using an alias. To trace messages sent to or from an alias, you need to use the alias in your query. This is less of a known issue and more about highlighting the change to existing behavior.
This feature is for Exchange Online-hosted mailboxes only. Messages to and from on-premises can be subject to rewriting the aliases on those servers.
Support in Outlook for Mac has not been added which will affect the preservation of aliases used in email threads

To provide feedback on the Preview (such as requests for additional features or functionality) we have set up an email to send those to: aliases-feedback[AT]Microsoft[DOT]com. We will monitor these to determine what functionality to invest resources into. Please note that we will not be individually replying to this feedback.

Outlook client feedback / features can also be filed (and voted on) on our new Feedback Portal. Please use the in-app support for Outlook Mobile issues, and regular support tickets can be opened for other versions of Outlook clients.

Here are some Feedback Portal items related to the aliases feature:

Let us know below what you think!

Exchange Online team

Updated Oct 21, 2024

Version 11.0

Microsoft

Joined April 19, 2019

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Exchange Team Blog

You Had Me at EHLO..

kenmich350
Copper Contributor
Jan 26, 2022
What about Outlook for macOS?
Satyajit321
Brass Contributor
Jan 29, 2022
The_Exchange_Team
This has been pending for long time. Useful feature, especially for M & A scenarios.

Recommendations:
1. However it would be good to have flexibility at an individual mailbox\group level instead of turning it on for everyone.
2. Do we have any mechanism in place to stop allowing certain domains, like mail.onmicrosoft.com or onmicrosoft.com to be used by the users.
3. It would be good to allow admins to control a list maybe using the Accepted Domain list, via a parameter, SendFromAliasAllowed True by default maybe for custom domains
4. Message trace will show Resolved and then Delivered like earlier or it will be now be directly delivered to Aliases (preserving the incoming alias), how the end-user will be able to tell, will it show <Email address removed> in Outlook
5. When internal users are sending email will it resolve to Primary or the Alias will be preserved on replies and new composed manually typed addresses within the Org
Sean_Stevenson
Microsoft
Jan 25, 2022
gauravkumra These changes are only being made for EXO. For hybrid, the alias preservation will last until/from the boundary of EXO. Any rewriting of aliases on-premises will continue.
RNalivaika
Iron Contributor
Feb 23, 2022
I hate that even microsoft started calling proxy adresses as alias. In exchange system alias is its own extremely important attribute. Many companies use it for building address lists and policies, dynamic distribution groups, lists and reports and much more, so it is not something obscure. And this confusion between alias and proxy address makes training junior techs more challenging. Exchange is complicated enough, so this confusion does not help.
faze9
Copper Contributor
Apr 26, 2022
The_Exchange_TeamHow does this work with regards to receiving replies on that alias. Because at the moment, in MS365, if we already have a group mailbox with same address, we are unable to add this as an alias for the user as it already exist. So, there's no real way to send using an alias and receive replies to a common mailbox.

Even after adding the user under "Send as" as well as "Read and manage (Full Access)" of the mailbox delegation, it still does not populate that shared mailbox address as alias in the list of 'Address to Send From/Manage List' on the user web app.

What we are trying to achieve here is:
We have multiple shared mailbox eg: sales@domainname, support@domainname etc.
And we have users who have access to these mailboxes.
The issue is, there are so many shared mailboxes that we end up having to add all of them to each client app thereby slowing down the app when each of them have to send/receive and store massive amounts of cached data.
So essentially, we want to be able to add only the 1 client user account on the client app.
And then all shared mailbox mails get forwarded to respective users.
And then users can use alias of that mailbox to reply to those forwarded messages without having to add each of those shared mailboxes on the client app.
faze9
Copper Contributor
Apr 27, 2022
JonLeCroyPlease have a look at the above questions I posted and let me know if you have any suggestion to share.
Ralph_Westland_SijnICT
Copper Contributor
Jun 22, 2022
We experience this problem related to this topic.
We have a Office365 user email address removed for privacy reasons with exchnage mailbox.
Then we have a shared mailbox email address removed for privacy reasons with send, send as and full control for the user email address removed for privacy reasons
If we send a e-mail from the shared mailbox, we receive the error not allowed to send mail as user email address removed for privacy reasons.
We created a new outlook profile for user email address removed for privacy reasons and addded via advanced settings email address removed for privacy reasons e-mail account
Reload the Offline addressbook but stil this issue exist.
Sugestions?? MS answerd that as a know issue that should be solved at this moment.

Cheers Ralph
Ralph_Westland_SijnICT
Copper Contributor
Jun 22, 2022
User one is in domain A
Shared mailbox is in domain B
Both domains are active in Office365
NeilSargent
Copper Contributor
Jul 27, 2022
Victor_Ivanidze
It certainly wasn't working for the desktop version of Outlook on May 31, when I posted my original comment. I still have the emails from System Administrator rejecting the test emails in my deleted items folder.

However it appears to be working now with Version 2205 (the previously working version of the Current Channel before I had to suspend updates following this month's Feature Gate fiasco with Microsoft Access).

The_Exchange_Team
When I say "working", I mean behaving in the same limited way as for the Outlook in the Web client that I highlighted in my post of May 31. There is still no control of the display name for the message sent using the alias email address. This limitation is so severe that it makes the new feature quite unusable.

For example: My primary mail box has a display name of “Neil Sargent” and email address of neil@workdomain. If I want to send and receive email from my (virtual) technical support department, I can create an email alias on my mailbox called support@workdomain. But if I send an email from that alias (using the current version of Outlook for the Web or Outlook for Windows), the recipient receives and email from “Neil Sargent <support@workdomain>”. However I want them to see the email as coming from “Company Technical Support <support@workdomain>”.

There appears to be no way to set the display name for the sent email, it always uses the Display Name field from my mailbox. If I enter “Company Technical Support <support@workdomain>” in the From field, the entered display name is stripped and ignored. When I send the message, it uses the correct alias email but ignores my entered display name. The recipient subsequently receives a message from “Neil Sargent <support@workdomain>”.

Using the mail box’s Display Name is worse than using no display name at all, since it undermines my attempt to send an email under a different persona to my primary mail box – which was the whole point of sending from an alias in the first place.

We need to be able to define a Display Name for each alias email address defined. Alternatively we need the option of entering the required Display Name in the From field when composing the message. Ideally we would like both, with the mail box defining a default display name but with the option of a manual override in the From address.

Kind regards
Neil Sargent
Victor_Ivanidze
Bronze Contributor
Aug 05, 2022
Hi Tom-irp,
contact MS support. As you are a global admin and exchange admin, you have to be able to turn on/off "turn on sending from aliases" checkbox.