EMAIL domain sharing in Rackspace Email (IMAP) to Office 365

Question

Hi,

We are planning to move 350 IMAP enabled mailboxes from Rackspace Email (IMAP) to Office 365.

I understand that on Office 365, I will have to add smtp domain first and create mailboxes in advance before executing the mailbox migration. However, I need some clarification on following:

1. Is SMTP domain sharing supported between Rackspace Email (IMAP) to Office 365?
2. We can configure internal relay for shared smtp domain in Office 365 but do we have same functionality available in Rackspace Email (IMAP)?
3. Can we do staged migration between Rackspace Email (IMAP) to Office 365?

Regards

Neeraj Kashyap

Answer 1

Hi @Neeraj Kashyap,

1. Are you intended to set up a third-party email coexistence with Office 365? If this is the case, yes, it's possible and you can refer to the official document below for more details:
   Plan for third-party email coexistence with Microsoft 365 or Office 365 and Azure Active Directory
2. I tried searching a lot but didn't find exact information about this query. Considering that this question is related to the feature in Rackspace Email, I'd suggest consulting the Rackspace support team as well for confirmation.
3. I am afraid not. A staged migration is recommended when the source email system is Exchange Server 2003 or Exchange Server 2007. For your scenario, it's recommended to use IMAP migrations. See the article below for more information about how to decide a migration path to Exchange Online.
   Decide on a migration path in Exchange Online

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