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I have a number of mail users (valid AD accounts with outside email addresses) and am in a hybrid Exchange environment with Office 365 and our on-prem server. The email addresses showing up in our on-prem system are just the external addresses we've assigned (user@anothercompany.com), as expected. But once the mail user gets synced to Office 365, it adds an internal address (user@ourcompany.com). Then later, when we have new users with similar names, that address has already been taken in O365 and we can't sync them. I also can't remove the extra addresses since the object is synched from on-prem, yet the additional addresses aren't assigned on-prem...

How do I stop O365 from creating internal email addresses for the mail users?

Thanks,

Keith
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  • Do the unwanted email addresses appear in the `mail` or `proxyAddresses` attributes for your users in AD? – BlueCompute Sep 20 '16 at 09:36
  • No they don't. Only on Office 365 after a sync. – Keith Sep 21 '16 at 19:08
  • Are you using any scripts or automation tools to create the users? When you look at the mailbox creation date - does it have the correct date or a much earlier one? – Jesus Shelby Sep 29 '16 at 13:14
  • Sorry for the late response - out of office for a while. No I'm not creating them with scripts or anything. Just creating them in AD Users and Computers. – Keith Oct 26 '16 at 18:02

2 Answers2

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I could envision a scenario where a cloud user is created and a local user and when you sync it does SMTP matching, and you are left with a synced users that then has that address.

You may also want to check the MetaVerse in the sync client and see what attributes it has stored for the users. If you notice it's in there, for some users but not others you may have to remove those users from sync fully (so metaverse is cleared), then re-sync them.

It is possible to make changes to cloud object, however, you first have to disable directory sync on the tenant, make your changes, then re-enable the tenant for syncing. If the email address re-appears it is almost certainly coming from on-prem.

Jesus Shelby
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  • I don't have the "Email Policies" option in O365 under "Mail Flow" like I do on-prem. Is there somewhere else to create policies? Also I can't modify these objects to change any settings because they're synced from my on-prem server. I talked to Microsoft for the better part of a day and they can't find the cause for it either... – Keith Sep 27 '16 at 21:05
  • my fault - I edited the answer to remove that. Address policies are not available in O365. – Jesus Shelby Sep 29 '16 at 13:11
  • Thanks but I'm less focused on fixing the ones that exist and more on stopping it from happening in the future. I believe I'm following the correct process for creating mail users/contacts but something is misconfigured and causing the email address to get assigned. Like the address rules on-prem are getting applied to O365 mail users or something. – Keith Oct 26 '16 at 18:05
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After much back and forth on this, Microsoft said that mail users (active accounts with outside email addresses) are not supported. I have a hard time believing this but that's what they say.

So my solution was to move the user accounts to an OU that is not synched to O365, thus deleting the user objects, and creating new contacts for each of these users so they are available in the address book. I deleted the email address from the user and added it to the contact. It took a few syncs over the course of a day for everything to fall into place and the duplicate warnings to stop but now it works great.

Thanks for the help.

Keith
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