Exchange Migration

Question

I need to migrate a client from an on-prem Exchange server to 365, they have already started using Microsoft teams with some Teams emails address having either developers@domainname.onmicrosoft.com or delvelopers@theirdomainname.co.uk and some of them have it the other way round either as a primary or alias, this was all done before I came on board with my present company. One of the mail enabled security groups on the on-prem Exchange server has the same email address as one of the Microsoft Teams Team. What will happen when I try and migrate this over to the Cloud?

Hope that makes sense

Any help much appreciated

Thanks

Answer 1

If they are duplicate email addresses, the sync of that email address will fail for the on-prem security group.
https://learn.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-syncservice-duplicate-attribute-resiliency

Better to clean that up now before syncing! :)

Answer 2

@Eric Henderson

One of the mail enabled security groups on the on-prem Exchange server has the same email address as one of the Microsoft Teams Team.

For Exchange on-premises group, it cannot be migrated, you need to remove from Exchange on-premises, then recreate it on Exchange online. Bue to this email address is used, so you cannot recreate it on Exchange online.

As AndyDavid said, when AAD Connect syncs, there will also exist issue due to duplicate email addresses. So, you need to remove one of them before sycing.

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