Exchange Server 2016/2019 On-Premises to Exchange Online
Boost growth with a scalable and cost-efficient solution
While Microsoft Exchange Server 2016/2019 is almost 10 years old, it is still a staple in the technology stack of many organisations, providing a robust and integrated communication platform with tried and tested infrastructure. Microsoft have announced that support for these versions is coming to an end in October 2025, therefore, now is the perfect time for businesses to move to a modern solution.
Embarking on a transformation from Exchange On-Premises to Exchange Online may feel like an upheaval, but the rewards are worth the change. Exchange Online, as part of Microsoft 365, offers a fully managed, cloud-based email solution with continuous updates, enhanced security, and improved scalability. In addition, you’ll benefit from seamless integration with other Microsoft 365 services, without the need for on-prem hardware and ongoing maintenance.
With years of experience in helping our customers migrate from all compatible versions of Exchange On-Premises to Exchange Online, we can help you too. Even for customers with strict compliance or regulatory requirements, we can help you find the ideal solution for your email communications.
Key features
Migrating your business to Exchange Online offers a number of key benefits, including costs, security, and more.
Cost efficiency
Exchange Online is licenced as a Software-as-a-Service (SaaS) subscription model, where you pay for licences on a per-user basis, making it more flexible and cost-effective.
Security
Microsoft provides continuous updates and enhancements to protect your email data from unauthorised access or data loss.
Scalability
Since Microsoft manage the Exchange infrastructure required to deliver the service, it can scale as required based on the needs of your business.
Reduced maintenance
There is no cost or effort required for hardware maintenance or operating system/application monitoring and patching, as this is Microsoft-managed.
Hybrid Approach
Using an Exchange Hybrid configuration enables a phased migration of mailboxes to Exchange Online, minimising disruption to your business.
Integration
Exchange Online integrates seamlessly with the other Microsoft 365 services, including Microsoft Teams, SharePoint/OneDrive for Business and the Microsoft Defender and Purview suites.
Luke Allinson
Foundation Capability Lead at Nasstar
"With Microsoft’s shift in focus to the Microsoft 365 platform, and the impending end of support for Exchange 2016 and 2019, now is the perfect time to transition to Exchange Online. It provides virtually unlimited scalability for your business, and together with Microsoft Defender for Office 365 and Microsoft Purview offers a comprehensive solution for hosting, managing, and securing your email data.
"It eliminates most of the headaches of managing Exchange Servers in your data centre; no more storage calculators, expensive hardware, patching windows or third-party interoperability nightmares - Microsoft manage the infrastructure so you don’t have to."
Related Services/Solutions
With the world moving towards a cloud-based future, many on-premises tools and services are facing challenges when it comes to integration, and on-prem Microsoft Exchange Servers are no exception. By migrating to Microsoft Exchange Online (which can be purchased via a dedicated subscription or as an included element within a Microsoft 365 plan), you can benefit from a better integration with other tools in the Microsoft solution portfolio, as well as improved security and scalability.
Our expertise
With a longstanding Microsoft partnership and multiple Exchange transitions of varying flavours under our belt, Nasstar is perfectly positioned to facilitate your Microsoft Exchange Server to Exchange Online migration. Whether you’re looking for a quick transition, or a full-featured migration with coexistence, we can help you prepare your business for Exchange Online, enabling and securing the service, and then moving your messaging data to the Microsoft cloud.
Nasstar supports worldwide businesses from different industries with tailored engagements, ranging from simple configuration projects to large-scale digital transformations. Our experience and expertise, combined with a deep understanding of business requirements and goals, allow us to customise a solution for your organisation, resulting in efficient and effective projects and the realisation of your short and long-term objectives through continuous collaboration.
Our consultants have a wealth of experience helping organisations move to Exchange Online, from simple small businesses to complex multi-nationals. We understand the challenges that you might face, the risks involved and the impact on your business and are ready to help you make your transition to Exchange Online and Microsoft 365 a success.
Why choose Nasstar?
A Microsoft Exchange migration may sound like a hassle you don’t need, but with Nasstar, we take all the stress out of it. Using our proven experience and processes, we can manage each step of the migration process; from planning, configuration, scheduling, service transition and business change all the way through to decommissioning your on-premises servers.
Nasstar’s Next Generation Managed Service completes the picture, providing comprehensive support capabilities either directly to your users or to your expert support team. Our rigorous Project Management methodologies ensure minimal disruption to your users and workflows so your business can continue to concentrate on what you do best.
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FAQs
Microsoft will continue to support on-premises Exchange via a new edition due to be released in Q3 2025. This coincides with the end of normal support for the current versions:
Exchange Server Subscription Edition (SE) is due to be released early Q3 2025, with Exchange Server SE CU1 scheduled for late Q4 2025. Once Exchange Server SE CU1 is released, all previous versions will be unsupported. This applies to organisations running Exchange Server fully on-premises, in a hybrid configuration or even those only using the management tools for recipient management.
While Microsoft are releasing Exchange Server SE to continue supporting organisations with Exchange on-premises, it is primarily aimed at large enterprise organisations. Minimum supported hardware specifications are very high, discouraging smaller-scale deployments, and version interoperability will be removed shortly after launch.
Unless your organisation is already running the very latest version of Exchange, it will require significant effort to remain in a supported configuration; it could include hardware procurement, major version transitions and non-trivial configuration changes. The cost of this project as well as the effort involved would likely be high and exacerbated by the compressed timescales.
The speed of a migration to Exchange Online can vary based on multiple factors, including the performance of the on-premises Exchange servers, network and internet link speeds/capacity, as well as the Microsoft cloud infrastructure itself. Is it also entirely dependent on the number and size of mailboxes in your environment.
Migrations using the native Exchange tools typically provide the fastest and most seamless end-user experience. Mailboxes are pre-seeded in batches to Exchange Online in the background; the length of this part of the process is dependent on the factors above. Once all mailboxes in the batch are fully synchronised, they can all be cutover to Exchange Online in a matter of minutes with minimal disruption; provided Outlook clients are configured correctly, a restart of the client is all that is required to connect to their new Exchange Online mailbox.
This process is consistent and will deliver good throughput for average mailboxes; Microsoft have observed up to 100GB per hour with multiple migration servers. As part of planning, Nasstar will help you to identify mailboxes that may take longer or require special consideration. These will typically be very large primary/archive mailboxes, or mailboxes with a very large number of messages; small mailboxes with lots of messages are slower to migrate than large mailboxes with fewer messages.
Yes, all these items in your mailbox will be migrated to Exchange Online, however you should be aware that there is no guarantee that 100% of your data will migrate successfully; this is due to your on-premises Exchange platform. There is always a risk that some items may already be corrupted and there is no easy way to check for them, but migration reports will show these as failed items. There is unfortunately no way to recover these messages, but typically the percentage of these items over the course of a full migration is low.
Exchange Online is generally considered to be more secure than Exchange On-Premises. Microsoft heavily invests in security of the Microsoft cloud platform to protect your data and your users accessing it.
- Modern authentication: While Exchange on-premises can be configured to support Modern Authentication, Exchange Online uses it by default. It provides significantly stronger authentication through standard protocols and enables features including Multi-Factor Authentication (MFA), passwordless logon and biometrics.
- Conditional access: The use of Modern Authentication also enables Microsoft Entra ID Conditional Access, which grants access to Exchange Online (and other cloud services) based on criteria that you define.
- Legacy protocols blocked by default: While you can still use POP3, IMAP4. and SMTP AUTH in Exchange Online, these now require modern authentication; legacy authentication for these protocols is now blocked. At time of writing, basic authentication with SMTP AUTH is still possible, however this is due to be removed in September 2025.
- Security updates: Microsoft manage the infrastructure required to run Exchange Online, and as a result they maintain the underlying operating system and application updates/patches. You don’t need to worry about update/patching windows or outages and can be assured that any security vulnerabilities are fixed quickly and with no disruption to the service.
If a migration is properly planned and scheduled, users may not even notice that their mailbox has been moved to Exchange Online (although obviously we should tell them!). The native migration process is designed to be almost seamless, and the pre-seeding and cutover operations mentioned earlier are what makes this possible.