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How to decide if a hybrid Exchange Server deployment is the right move

Here's a closer look at hybrid Exchange Server deployments, the pros and cons of on-premises deployments and myths about Exchange in the cloud.

This is part two of a series highlighting the best Exchange deployment options for your organization. Read part one here.

The pros and cons of hybrid Exchange Server deployment models

The most difficult questions when adopting a hosted or hybrid Exchange Server model require IT admins to examine the pros and cons of each format and how they relate to each organization's requirements and governance standards.

Let's take a look at the pros and cons of on-premises deployment, a cloud-based environment and the hybrid Exchange Server model, as well as some common misconceptions about hosting your Exchange Servers with a third-party cloud provider.

On-premises deployment. This scenario lets you maintain full control of your mail environment, including the hardware, software, backups and recovery. You also control the allocation of the mailbox, each user's mailbox size and the message size of what can be sent and received.

An on-premises arrangement allows you to control the third-party tools you integrate with your mail environment. Your email data is fully within sight, which lets you know who can access it and which security controls are in place. Another benefit is the freedom to schedule maintenance and upgrades when they're most convenient. This keeps uptime within your sphere of influence.

As for disadvantages, on-premises Exchange can be more costly than cloud-based alternatives because you own and maintain the hardware and software. You also need to maintain a high level of in-house skill, especially if you have a high-availability environment spread across several data centers.

A high-availability infrastructure requires a deep understanding of networking, clustering, database log replay, resilient client access and transport servers. Running multiple in-house Exchange servers also contributes to your organization's overall carbon footprint because you need to power and cool servers and associated networking equipment.

If you run Exchange on-premises, you need to maintain the environment and perform all of the planning required to move between rollups and service packs.

Off-premises deployment (with Office 365). The primary advantage of an off-premises Exchange deployment is that you can reduce overall capital, revenue costs on hardware and software, and staff/administration costs. As for availability, a cloud-based provider often guarantees 99.9% uptime. Off-premises Exchange lets you connect from almost anywhere, which promotes mobile working and business continuity.

Other benefits include having hygiene and other third-party services integrated into the overall subscription cost of the service. Organizations can take advantage of other Office applications with high degrees of integration from a single provider based on cost-effective subscription plans.

One downside of cloud-based Exchange is that you no longer have full control of your data. This is paramount if your organization has strict data protection rules, including those governing how certain email messages must be routed and stored. If you migrate to Office 365, your data could reside in any number of data centers around the world, meaning you may not be able to guarantee these compliance requirements are met.

When you need to integrate other business systems into your environment, you may be limited in what you can achieve if you don't run Exchange on-premises. For example, certain customer relationship management applications require integration with a mail system through an application programming interface (API) or a physically installed software component.

Hosted Exchange has other limitations, including potential loss of control over subscription costs, a lack of clarity on integrating data back into an organization if you terminate a contract, and the need to invest in more robust networking infrastructure to ensure fault tolerance should your primary link to the Internet fail.

Hybrid deployment. A hybrid Exchange Server deployment potentially offers the best of both worlds. You can maintain some control over security, integration and data. This type of deployment allows for a large environment's staged migration at a controllable pace, letting you scale to a utility model where the company's monthly or yearly expenditure is proportionate to the number of mailboxes in use. It also lets you evaluate a hosted model without committing your entire user base.

The downsides include the complexity to set up and manage the infrastructure, the inability of the hybrid model to create short-term staff savings, software and hardware costs, and the chance you'll pay for in-house and off-site infrastructure.

Common email hosting myths

So what about those perceptions about cloud or hosting scenarios? Some are more fiction than fact.

Hosting means you lose sight of your data. This isn't exactly true. You can see your data day to day, and if you adopt a hybrid model, you can move data between local Exchange servers and the cloud. You never lose ownership of your data; it's just not where you're used to accessing it.

Hosting is less secure. This is not really true. Most hosting providers have greater control over their systems' security than what a business can locally provide. The concern is how to secure the communication between your hosting company and the client endpoint. In many cases, this is via the Secure Sockets Layer, which is no less secure than externally providing Outlook Web Access.

Hosting is not reliable. No computer system is 100% reliable, and when you move to the cloud, your focus will change from high availability for your own mail servers to redundant network links. Providers have made extensive investments in uptime since their business viability on delivering on their promises to provide services. These investments will more than likely be more extensive than what most organizations can afford on their own. This means reliability problems are infrequent and usually solved in less than an hour.

Hosting means all of my problems go away. This is not always the case. Businesses that want to reduce administrative overhead and costs should remember that even the hosted route requires account management administration and maintaining the organization's cloud environment. These demands are less intense than an on-premises setup, but it is a continued requirement.

Making the decision about how to run an Exchange deployment isn't simple, but your choice should be built on a solid business case. Look at your options and run the numbers. See which alternative makes sense for your business now -- and five years from now.

About the author:
Andy Grogan is a multiple recipient of the Microsoft Exchange MVP award (2009-2013). He is based in the U.K. and has worked in the IT industry for the last 16 years, primarily with Microsoft, HP and IBM technologies. His main passion is Exchange Server, but he also specializes in Active Directory, SQL Server, storage solutions, technology strategy and technical leadership in large-scale enterprises. He currently works for a large county council in Surrey as its technical delivery manager and supports 15,000 customers on more than 240 sites. Visit Andy's website,

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