New type of addresses in Office 365 (SPO alias)

Few days back, a new address type suddenly appeared for all users in Office 365. The address if prefixed with the SPO string and looks like this:

122516 1042 Newtypeofad1

I first stumbled upon this info in a thread on the Office 365 Community forums. After some digging around, I wasn’t able to find any info about this so I turned to the MVP lists. Tony Redmond’s educated guess was that the new address has something to do with the switch to using EWS for sending any SharePoint related notifications. Later on, this has been half-confirmed by Microsoft, by referring us to the following KB article. Unfortunately, this article is a bit short on details on what exactly the address is needed for, as EWS impersonation can simply work with a regular SMTP address. Maybe it’s deliberately chosen so it doesn’t interfere with the ‘regular’ SMTP addresses, as this method is also used for impersonating users without mailboxes (however that should work). In any case, details are scarce at this point, and the above article is all we have – take it or leave it 🙂

Now, here’s what we do know about the SPO addresses so far. They are automatically added to any licensed mailbox, so no shared or room mailboxes should have them. It also seems that those addresses are not added immediately upon user creation, and might appear only after the user has explicitly shared a document. The addresses do appear in the GAL, as shown in the screenshot above, and can be exposed via PowerShell just as regular SMTP addresses. For example, the following cmdlet can be used to filter out all mailboxes that do have a SPO address provisioned:

Get-Mailbox -Filter {EmailAddresses -like "SPO:*"}

The format of the address is the following: an SPO prefix, followed by an underscore and a GUID, which does not seem to correspond to the objectID in Azure AD, nor any of the other GUIDs we can expose. It does differ from user to user, so it’s perhaps some “internal” SharePoint GUID? Anyway, the last part of the address, just after the @ sign is the tenant GUID, again prefixed with SPO and underscore.

The address can be edited, removed or added just like a regular SMTP address, however for objects synced from the on-prem AD this will not be possible (although they do get the address as well!). Another interesting fact is that the address is not visible in Azure AD (via the MSOL cmdlets or the Graph API), which in turn makes it hard to confirm its existence for any non-mailbox users.

If someone does figure out more details about this, let me know please 🙂

5 thoughts on “New type of addresses in Office 365 (SPO alias)

  1. LLORT in a mirror says:


    Not sure about you but did you find it by clicking on the word thread with the link that Vas provided for us in the article he has written about the threat he provided the link for. It . doesnt work anymore so I’m wondering did you find it that way and then kindly give us the answer or did you find it yourself and didnt notice that Vasile is the first responder to the question asked.

    I am wondering because I have been unsuccessful in the past at finding answer on the forum let alone being able to help others and giving them advice on the subject they are educating us about.

    Would be great to know because I have lots of questions still unanswered by MS Techs and you seem like a flipping genius at finding helpful answers

    Thanks for the help

  2. Travis says:

    I noticed this SPO entry show up in our environment this week. However we do not have any sharepoint licenses. We only have Exchange Online Plan 1 – The most basic Plan.

    1. Rune-Coder says:

      O365 Exchange Online Plan 1 contains regulary the OneDrive-cloud storage function.
      OneDrive and files saved to it, are managed on sharepoint-websites.
      So basically OneDrive is Sharepoint and if someone saves files to OneDrive (and share them) it is most likely that this user get a SPO adress.

  3. Gandalf says:

    If you are still looking for the answer, I found it in the forum, where a support agent said:
    The SPO type email address indicates that it is related to SharePoint Online features.
    The fact is that it only appears on objects with a SharePoint Online license confirms this.
    Currently, there is no official documentation shows that describes the function of this new type email addresses.


    1. Tom Kinelly says:

      LOL The forum thread you found it on is the exact thread Vasiles article is about.

      This article he has written is based on the culmination of the info and conversations had here by a number of very well versed techies with a great willingness to share their knowledge with others and Vasile responds directly to the post you have quoted.

      He must be banging his head against the wall when he read your response!!!

      Brilliant!!!! Big smile right now! stopped chuckling!!


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