Hybrid Microsoft 365 Migration — Exchange Server to Exchange Online
IT Partner's Hybrid Microsoft 365 Migration from your own Exchange Server integrates an on-premises Exchange organization with Microsoft 365 Exchange Online using Microsoft's Hybrid Configuration Wizard, then migrates mailboxes through native migration batches. Hybrid works as a migration method or as a permanent coexistence state. The service covers analysis, Entra ID Connect synchronization with password sync, user informational letters, mailbox migration, migration-related break-fix support, and a project closeout report — currently offered free (Microsoft sponsored) as a 2-week engagement.
What this engagement is
A hybrid deployment extends an existing on-premises Microsoft Exchange environment to Exchange Online in Microsoft 365, providing integration between the two organizations — usable as a migration path or as a long-term coexistence state. A typical engagement works from a single-forest, single-domain organization with an Exchange server such as Exchange 2016 installed. IT Partner deploys and configures the required Entra ID Connect server with password synchronization, so users sign in to both their on-premises network account and Microsoft 365 with the same credentials. IT Partner then completes the hybrid prerequisites and runs Microsoft's Hybrid Configuration Wizard, selecting the options — including minimal or full hybrid — that match your mail flow and coexistence requirements. In the resulting topology, users sign in to the on-premises and Exchange Online organizations with the same username and password; mailboxes on-premises and in Exchange Online share the same email address domain; outbound mail is delivered to the Internet by the on-premises organization, which controls messaging transport and relays for Exchange Online (centralized mail transport) where that design is selected; on-premises and Exchange Online users share calendar free/busy information; organization relationships enable cross-premises message tracking, MailTips, and message search; and the same URL serves mailbox connections for both on-premises and Exchange Online users. Mailboxes then move to Exchange Online through native migration batches, which users experience with minimal disruption.
Success criteria
What you receive
How the work unfolds
Confirm scope, schedule, points of contact, mailbox counts, high-risk users, access requirements, communications approach, and the target hybrid migration timeline.
Review the on-premises Exchange, Active Directory, DNS, certificate, mail flow, and mailbox inventory readiness for a hybrid Exchange Online migration. Identify blocking issues, large mailboxes, and configuration items that must be corrected before migration.
Configure or validate Entra ID Connect synchronization, including user synchronization and password synchronization. Confirm Microsoft 365 domain verification, user matching, licensing readiness, and directory synchronization health.
Define the migration batch approach, pilot users, migration schedule, user communications, DNS and transport changes, validation checkpoints, and issue escalation process. Confirm whether hybrid will be used only for migration or retained as a longer-term coexistence state.
Create and validate the hybrid migration endpoint and initial migration batches, then begin mailbox moves to Exchange Online according to the approved plan. Monitor synchronization progress and address migration errors related to mailbox readiness or connectivity.
Validate migrated pilot or batch mailboxes for mailbox access, message data, send and receive mail flow, free/busy visibility, Outlook/Autodiscover behavior, Exchange Online Protection behavior, and required transport rules.
Coordinate the approved DNS cutover, including MX and related mail-routing records as required by the agreed design. Validate inbound mail flow after DNS propagation and confirm any hybrid or centralized transport requirements remain aligned with the final mail flow design.
Complete remaining mailbox batches, perform final synchronization, complete cutover activities for migrated users, and resolve migration-related errors that occur during the final move window.
Perform post-migration validation against the success criteria, confirm mail flow and user access, review outstanding issues, provide migration-related break-fix support, and prepare the project closeout report.
Prerequisites
Who does what
IT Partner
- Analyze the current Exchange On-Premises solution
- Prepare the current configuration of Exchange and Active Directory for synchronization
- Set up synchronization of users and passwords
- Provide informational letters for users
- Migrate mailboxes
- Provide break-fix support related to migration issues
Your team
- Coordinate Client resources and staff schedules
- Provide a dedicated point of contact responsible for working with IT Partner
- Provide access to physical and virtual servers and/or systems and services as needed. Provide remote and/or physical access to facility and systems required to complete the work
- Configure workstations and mobile devices
- Perform changes to internal and external DNS, as required
- Assist with identification of high-risk users (top executives and VIP users, users with 50 GB mailboxes or larger and/or 30 GB deleted folders or larger)
- Coordinate any outside vendor resources and schedules
- Configure all network equipment, such as load balancers, routers, firewalls, and switches.
- Review and approve engagement deliverables in a timely manner
What's not included
Limitations & technical notes
Frequently asked questions
What is IT Partner's Hybrid Microsoft 365 Migration from your own Exchange Server service?
It connects your on-premises Exchange organization with Microsoft 365 Exchange Online — identity synchronization, mail flow, and collaboration features — and migrates mailboxes through Microsoft's native migration batches. Hybrid can serve as the migration method or remain as a longer-term coexistence state.
How much does the hybrid migration cost, and how long does it take?
The service is currently offered free (Microsoft sponsored) and runs as a 2-week engagement. Scope is confirmed in writing before work begins.
What is included in the service?
Analysis of the current on-premises Exchange solution, preparation of Exchange and Active Directory for synchronization, Entra ID Connect setup with user and password synchronization, informational letters for users, mailbox migration, migration-related break-fix support, and a project closeout report.
What prerequisites are required before starting?
A Microsoft 365 tenant with Exchange Online licenses, access to your email domain DNS zone, and a full installation of Exchange 2010, 2013, or 2016 with a valid UCC SSL certificate. The hybrid deployment depends on a working on-premises Exchange environment, licensed destination mailboxes, and DNS changes for mail routing.
How does identity and password synchronization work?
IT Partner deploys and configures an Entra ID Connect server with password synchronization, so users sign in to their on-premises network account and their Microsoft 365 account with the same username and password.
Is the hybrid set up with Microsoft's Hybrid Configuration Wizard?
Yes. After the hybrid prerequisites are completed, IT Partner runs Microsoft's Hybrid Configuration Wizard and selects the appropriate options — including minimal or full hybrid — based on your mail flow, free/busy, and coexistence requirements.
Will users keep the same email address domain after moving to Exchange Online?
Yes. The hybrid topology is designed so on-premises and Exchange Online mailboxes use the same email address domain, which lets users move to Exchange Online without a new email domain.
How is mail flow handled during the migration?
The hybrid design determines mail flow: with centralized mail transport, outbound mail is delivered to the Internet by the on-premises organization, which relays for Exchange Online. The implementation plan includes the MX record change to Microsoft 365, and the final inbound and outbound design is confirmed during migration planning.
What hybrid coexistence features are configured?
Shared calendar free/busy between on-premises and Exchange Online users, organization relationships for cross-premises message tracking, MailTips, and message search, and a common URL for mailbox connections on both sides.
Will users be able to access mail on desktop PCs, phones, and tablets after migration?
Yes — that is one of the success criteria. Configuring workstations and mobile devices, however, is the client's responsibility: IT Partner's scope does not include desktop software settings or device configuration.
Can Unified Messaging be used with this hybrid migration?
No — Exchange Unified Messaging (UM) features are not available in a hybrid solution in conjunction with Microsoft 365. If UM is present in your infrastructure, alternative voicemail arrangements should be reviewed with IT Partner before migration.
What support is provided after the mailbox migration?
IT Partner provides break-fix support for migration-related issues and completes post-migration validation against the success criteria. The engagement ends with a project closeout report covering final status, acceptance criteria matching, outstanding issues if any, and the final budget.
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