Create email aliases in Office 365 DirSync/AADConnect environment

Issue: You have an AD Synchronized (DirSync or Azure AD Connect) Office 365 environment and need to add additional email aliases to an Office 365 Mailbox.  This could be in a situation where you have a generic address you’d like delivered to someone,, or in the event an employee doesn’t use email and all their mail should be delivered to their assistants mailbox.

Application: This article applies to DirSync, Azure AD Connect or ADFS federated environments that are not running on-premise Exchange (“Hybrid Mode”) and therefore cannot use an on-premise Exchange to add email aliases

Solution: On a DirSync’d Office 365 environment, email address changes are managed in (on-premise) Active Directory.  Note: this solution may also apply to Azure AD Connect, the successor to DirSync.

1) To avoid confusion, if any AD accounts currently have the email address assigned that you want to add as an alias to another Office 365 mailbox then you should remove it from those AD accounts.



2) Add the aliases to the destination AD account that you want the mail delivered to

Windows 2008R2 DC: Open Active Directory Users and Computers (ADUC), click view > advanced features, doubleclick the users account in the list of users (not through Find) and click the Attribute Editor tab


Pre 2008 R2 DC use ADSIedit:
Start > Run and type adsiedit.msc
Expand Default naming context
Expand DC=DOMAIN,DC=COM,OU=Company_Users
Right click the user you want to edit and click Properties.

3) Find the variable proxyAddresses
When you add new e-mail aliases, you need to make sure that your primary e-mail address is included and prefaced with with upper-case ‘SMTP:’.  Your aliases, aka, secondary addresses should be prefaced with a lower-case ‘smtp:’.  For example, I want my primary e-mail address to be

In the proxyAddresses attribute use the following format:
to make an alias I will specify lower case “smtp:” like this: “”


Note: If you are troubleshooting an email address assignment issue you mail want to look at the ‘mail’ attribute as well.

4) To make the changes effective immediately, run a manual DIRSYNC using PowerShell on your DIRSYNC Server to synchronize the changes up the Office 365 cloud (by default automatic directory synchronization is every 2 hours).


14 thoughts on “Create email aliases in Office 365 DirSync/AADConnect environment

  1. ijwrighty

    I don’t believe this to be a supported method. The correct method is to setup “Remote Mailboxes” and then manage everything from the Exchange console/ Web Console.

  2. Durgesh Bhat Kalya

    Thank you Chris. Looks like MS is not so supportive of officially publishing such a procedure but it is the only way (easy way). I was stumped when I encountered this was missing on their KB articles.

    Thanks Again!

    1. Chris Harris Post author

      Thanks for your compliments Durgesh. Are you running Azure AD Connector or DirSync? I’d like to confirm if my instructions apply to Azure AD Connect (the successor of DirSync). Thanks!

  3. Joey B

    Chris, thanks for the great write up, I can now add aliases to email accounts.

    The contacts that I have added aliases to are now showing two send email options under their contact card from Outlook. Do you know how to have it hide the alias?

  4. Thomas


    How would one change the primary SMTP address or what Microsoft o365 calls the Reply address?


  5. Chris Harris Post author

    Hi Tom, have you tried checking out the distribution groups in the Office 365 Admin Portal, you may be able to manage distribution groups and their email addresses from there. Please post again letting me know.

  6. Tom Scott

    Any way to add alias’s to distribution groups?

    IE: Created an “Info” Distribution group in my AD.. I have 3 domains / email addresses that I want that group to have but it doesn’t have that attribute like a user object does..



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