Convert on-premise AD users to MailUsers (Exchange online)

Question

Hello,

We have an on-premise AD environment with Exchange online (365).  We have a lot of AD users that we wish to have external email addresses (outside of our domain).  These users are customers, contractors, etc.  However, after searching and testing exhaustively, we can't seem to find a way to convert these AD users to MailUsers, or at least have them appear in the GAL with their external addresses (instead of blank currently).

We found a post that would essentially get us the result we want, with the caveat that we would be creating new users from scratch.  (Create a MailUser in Exchange Online, then create AD user on-premise with same SMTP address.  ADSync would then "bind" the two and make the AD account that master moving forward.)

https://support.microsoft.com/en-us/help/2641663/how-to-use-smtp-matching-to-match-on-premises-user-accounts-to-office

However, we have many AD users in our AD that we wish to have external addresses and do not want to have to delete them all to follow the process outlined in the link above.  We've also tried modifying some of the AD attributes such as msExchRecipientTypeDetailswith no success.

Does anyone know of a way to accomplish this?

Thanks in advance!

Answer 1

Hi Barry,

We have read the article you posted regarding SMTP matching but that only works for brand new contacts or users.  We have a many AD users that we would like in the GAL, but we cannot make the contacts in Exchange online because we get a duplicate user error.  If it's a brand new user, we can create the Mail User in Exchange online and then make the on premise AD user.  This method works fine, but not for AD users that exist already.

We want existing, on-premise AD users to become mail users with external email addresses so they show up in the GAL.  We do not have on-premise Exchange.

Answer 2

Hi Mattwdaniels,

Let us know any updates when you are free.

Thanks,

Barry

Answer 3

Hi Mattwdaniels,

Thanks for your reply.

If there are both Mail Users in the On-Premise AD environment and Office 365, their SMTP addresses are the same, you can use SMTP Match to match them. Note: There should be no relationship between the On-Premise AD account and Office 365 Mail user. You can refer to this article to perform the steps: https://support.microsoft.com/en-sg/help/2641663/how-to-use-smtp-matching-to-match-on-premises-user-accounts-to-office.

Meanwhile, Could you tell us the finally requirement you want?

Thanks,

Barry

Answer 4

Hi Barry,

We've reviewed that article before.  We do not have any on-premise Exchange servers.  We just have on-prem AD, Azure AD and Exchange Online.

Answer 5

Hello Mattwdaniels,

According to your description, we know that you don’t add the external email address as a MailUser in your local server. To convert a local user to a mailuser, please refer to this article: https://technet.microsoft.com/en-us/library/aa996549(v=exchg.160).aspx

If the external users’ email addresses exist in both local server and Office 365 cloud, and there is not relationship between the local account and the Office 365 online account, you can run an Azure AD Connect to match them: Integrate your on-premises directories with Azure Active Directory. After that, you will have a local MailUser and a corresponding Office 365 MailUser. Please tell us if this meets your requirements. If you have any further questions, please feel free to contact us.

Thanks,

Barry