Keep calm and SendAs a Proxy Address

Keep calm and SendAs a Proxy Address

5 / 5 ( 1 vote )

I’m gonna channel the great Etta James:

Ok, I’m back.

I’ve been waiting for this feature for what seems like an eternity–the ability for a mailbox that has multiple proxy addresses to send from any of those addresses.


As most of you probably know, a mailbox can have a whole lot of additional SMTP addresses associated with it (a mailbox can have up to 400 proxy addresses stamped on it).  When I was in Microsoft Consulting Services, I frequently had customers that had hundreds of email domains associated with their tenant (each usually representing a unique brand or business unit), and mailboxes could have proxy addresses for dozens of those. This was an infuriating problem–they could receive as any one of the addresses, but all outgoing mail would always be stamped as the primary SMTP address.

Not anymore.

We have arrived.

Under the hood

First, I’ll take a step back (in the off-chance you don’t know what I’m talking about).  You can see a mailbox’s proxy addresses in a number of places (depending on where your user identity is sourced).  Proxy addresses will appear in Exchange Server and Active Directory (if you’re in a hybrid configuration and have synchronized your directory to Azure AD) as well as in Exchange Online.

For example, I’m going to take a look at my synchronized account in one of my test tenants:

Not to worry–if you’re not a PowerShell aficionado, you can still see the same data from the Exchange Online admin center:

The entries in bold are the primary SMTP addresses for that particular proxyAddress type.

Updating your tenant

Making the shift isn’t automatic (yet) and isn’t in the GUI (yet–if ever). So, you’ll have to head to Exchange Online PowerShell.

Once connected, you’ll want to check/modify the Organization config:

Get-OrganizationConfig |select "Send*"

As you can see, it’s set to $False currently.  Enabling the feature will require you to update this setting to $True.

Set-OrganizationConfig -SendFromAliasEnabled $True

After you’ve made that update, it’ll have to bake for a while.

Testing it out

Timer’s done! Let’s check it out!  We’ll look at the experience in both Outlook and OWA client interfaces.


This one’s pretty straightforward–it works like it always has.

  1. Compose a new message.
  2. Use the ellipsis to expose the additional options, and then select Show Fields > From.

  3. With the From field exposed, you can now enter one of the aliases on your mailbox.
  4. Type in one of your proxy addresses and click OK.
  5. Continue drafting your message and send it.

Congratulations! You get a sticker!

Outlook Web App

The process to do it in Outlook Web App is very similar.

  1. Log into Outlook Web App (
  2. Begin to compose a message.
  3. Select the ellipsis at the bottom of the message to expose the menu and select Show From.
  4. Click the From field in the message and select Other email address…
  5. Type in one of your proxy addresses and then press Enter or tab away from the field.
  6. Continue drafting your message and send it.

In either case (whether via Outlook or OWA), the recipient should see the updated sender in the FROM field:

Secret Bonus Time

Back in August 2020, we also (without much fanfare) released support for something known as + addressing (plus-addressing).  Google has had this feature for a bit (and it’s quite nice, I might add), so I was super excited to see us get it out of the backlog and into production.  If you’re not familiar with it, here it is in a nutshell:

You can append “+WhateverTextYouWant” after the left-hand side of your email address and before the @ sign.  So, if your normal address is, you can tell mailing lists or whatever to send to  It’s dynamic, and no work needs to be done from the admin side (aside from making sure the feature is enabled, as shown below).

You can use this nifty Send-As Proxy with plus addresses as well, with a teensy caveat.

While receiving with a +address is dynamic and totally fine, in order to send with a +address, the +address you send from has to be stamped on your mailbox like a normal proxy (so yes–it kind of defeats the overall purpose of the +addressing, but I digress).

To make sure the +addressing feature in your tenant is evailable, all you need to do is have the AllowPlusAddressInRecipients property set in your OrganizationConfig.  You can see your current status by running:

Get-OrganizationConfig | Select *Plus*

If you created your tenant after August 2020, it should already be enabled.  If your tenant pre-dates that, you’ll need to update your configuration accordingly:

Set-OrganizationConfig -AllowPlusAddressInRecipients

Then, follow the above steps with your client of choice.

Keep calm and Send As a proxy!

Published by Aaron Guilmette

Helping companies conquer inferior technology since 1997. I spend my time developing and implementing technology solutions so people can spend less time with technology. Specialties: Active Directory and Exchange consulting and deployment, Virtualization, Disaster Recovery, Office 365, datacenter migration/consolidation, cheese. View all posts by Aaron Guilmette

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