Questions regarding a pilot to Office 365 from an On-Prem Lotus Domino

Occasional Contributor

Hello experts,

we're about to start a pilot as part of planning a migration to Office 365 for a customer which is currently using an On-Prem Lotus Domino. We will be piloting just a handful of the users on the On-Prem Lotus Domino and this will be our first migration to Office 365 from an On-Prem Lotus Domino.

We have a clear understanding of all the DNS settings we need to have in place in order to start the pilot as we set up Hybrid other times in the past.

I would like to check with you if our plan below makes sense to you and if out of courtesy you could provide additional observations/recommendations:

1 – MX records will still be pointing back to the On-Prem Lotus Domino and not to Office 365
2 – we'll configure forwarding to ensure that email intended for the pilot users will be forwarded correctly to Office 365 using the domain
3 – we've configured the domain as an Internal Relay (instead of Authoritative) in Office 365 as Exchange Online is not going to have knowledge of all the mailboxes on the On-Prem Lotus Domino
4 – we're planning on using BitTitan to migrate all mailboxes data in Office 365

In order to make sure that mail flow is working correctly between Office 365 and the On-Prem Lotus Domino, we are planning to:

1 – set up a connector in order for Office 365 to trust email coming from the On-Prem Lotus Domino. At least initially, most likely we will specify the public IP address of the Internet-facing On-Prem email server as our customer does not currently have a certificate from a third-party trusted CA installed on the On-Prem email server
2 – as we will not be setting up Hybrid, my understanding is that Internal Relay will deliver back to the On-Prem mailboxes using the MX record and that, as a result, a connector in order for Office 365 to deliver email back to the On-Prem Lotus Domino is not strictly needed. Is my understanding correct ?

Any additional observations/recommendations on this matter will be greatly appreciated.

Thanks and Regards,


2 Replies
best response confirmed by mrizzi2 (Occasional Contributor)

Yes, assuming I understand the intended setup correctly, connector is not strictly needed. You can however still use one in order to secure mail flow.

Hello Vasil,

thank you for taking the time to reply to my question.