Pros and Cons of migration to Exchange Online and Office 365

Here is something I wrote up for a piece of a much bigger documentation. It is pretty generalized stuff but I tailored it more towards Exchange Online, the client, and the more realistic issues I see rather than stuff that is uncommon or minimal in impact. I realize there is stuff that isn’t here, but there could never be a complete list.


  • Drastically cut Messaging Infrastructure:

Ongoing Hardware Costs (Servers, Anti-Spam Appliances, Storage)
Ongoing Software Costs (Server licensing, Exchange licensing, CAL’s, Microsoft Office licensing)
Unreliability (Added DR costs, DAG costs, Bandwidth, Maintenance)
Overall Management Time & Cost
Overall Maintenance Time & Cost

Ensure Exchange high-availability (current quarter 99.99% uptime)

Built-In Spam and Malware Protection with Exchange Online Protection

50GB mailboxes standard – E3 adds unlimited In-Place Archiving, eDiscovery, Legal Hold, Rights Management, DLP, Encryption

Last mail-migration ever. Always latest and greatest backend and client software

Additional Benefits

OneDrive For Business – provides a place in the cloud where you can store, share, and sync your work files. You can update and share your files from any device with OneDrive for Business. You can even work on Office documents with others at the same time.

E3 adds Office ProPlus, Skype For Business – enable the ability to work, communicate and collaborate from anywhere on any device. Always latest and greatest software.

E5 adds Skype For Business Cloud PBX with PSTN Calling – Cloud PBX moves the call control and features normally found in an on-premises deployment into the cloud, theoretically leaving only client software and desktop devices on the customer premises. You can use existing TDM and SIP Trunks to access the PSTN on premises or port existing numbers to Microsoft’s cloud. This feature set also adds Broadcast Meetings and PSTN Conferencing.

Other added E5 features
⦁ Advanced analytics with Power BI and Delve Analytics
⦁ In-place, Advanced eDiscovery
⦁ Advanced security with Advanced Threat Protection and Customer Lockbox
⦁ Enhanced visibility and control of your Office 365 environment


  • Subscription Based – Might not see total value with E3 licensing if Office Suite was recently upgraded.


  • Less Flexible Infrastructure – On a case by case basis there may be some reduced customization and configuration in terms of hardware or 3rd-party products since Exchange Online is an IaaS.


  • Data Privacy – Some private business data will live on Microsoft’s servers. For certain use cases it might be even impossible (legal reasons), to have your data hosted outside your organization. Microsoft does have federal and financial options that may be able to satisfy some of the more security sensitive business areas. You can also use the Hybrid solution to keep applicable mailboxes On-Premises.


  • Reconfiguration – In Non-Hybrid migrations, devices may require initial reconfiguration to point to Microsoft Online servers instead of On-Premises.

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