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I have a hybrid deployment with Exchange 2010 on premises, AD on prem, running ADConnect to sync all identities to Azure/Office 365. &nbsp;<br />
<br />
I have exchange 2013 boxes; CAS, ARR Proxy and Edgesite servers and have migrated all of my mailboxes to Exchange Online.<br />
<br />
My question is, do I have to keep at least one or two of the exchange 2010 exchange servers in this setup? &nbsp;I still have about 10% of mailboxes on premises that are mostly service account mailboxes. &nbsp;I don't have any DLs migrated, these are still on prem. &nbsp;<br />
<br />
What is needed to retire the 2010 exchange boxes, migrate DLs? &nbsp;Migrate the remainder of mailboxes? &nbsp;Is there anyway these can be moved moved to one of the 2013 CAS servers and attach a database so as not to consume a license? <br />
<br />
Or do one or two need to remain as long as I'm in hybrid coexistence mode and always need to remain?<br />
<br />
Thanks Experts!
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I have a hybrid deployment with Exchange 2010 on premises, AD on prem, running ADConnect to sync all identities to Azure/Office 365.  

I have exchange 2013 boxes; CAS, ARR Proxy and Edgesite servers and have migrated all of my mailboxes to Exchange Online.

My question is, do I have to keep at least one or two of the exchange 2010 exchange servers in this setup?  I still have about 10% of mailboxes on premises that are mostly service account mailboxes.  I don't have any DLs migrated, these are still on prem.  

What is needed to retire the 2010 exchange boxes, migrate DLs?  Migrate the remainder of mailboxes?  Is there anyway these can be moved moved to one of the 2013 CAS servers and attach a database so as not to consume a license? 

Or do one or two need to remain as long as I'm in hybrid coexistence mode and always need to remain?

Thanks Experts!

Exchange Hybrid / Office 365

Windows PowerShell is a task automation and configuration management framework from Microsoft, consisting of a command-line shell and associated scripting language built on the .NET Framework. PowerShell provides full access to the Component Object Model (COM) and Windows Management Instrumentation (WMI), enabling administrators to perform administrative tasks on both local and remote Windows systems as well as WS-Management and Common Information Model (CIM) enabling management of remote Linux systems and network devices.

Powershell

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

Office 365 is a group of software plus services subscriptions that provides productivity software and related services to its subscribers. Office 365 allows the use of Microsoft Office apps on Windows and OS X, provides storage space on Microsoft's cloud storage service OneDrive, and grants 60 Skype minutes per month. Office 365 includes e-mail and social networking services through hosted versions of Exchange Server, Skype for Business Server, SharePoint and Office Online, integration with Yammer, as well as access to the Office software. All of Office 365's components can be managed and configured through an online portal; users can be added manually, imported from a CSV file, or Office 365 can be set up for single sign-on with a local Active Directory using Active Directory Federation Services.

Microsoft 365

Active Directory (AD) is a Microsoft brand for identity-related capabilities. In the on-premises world, Windows Server AD provides a set of identity capabilities and services, and is hugely popular (88% of Fortune 1000 and 95% of enterprises use AD). This topic includes all things Active Directory including DNS, Group Policy, DFS, troubleshooting, ADFS, and all other topics under the Microsoft AD and identity umbrella.

Active Directory

Microsoft Azure is a cloud computing platform and infrastructure for building, deploying and managing applications and services through datacenters. It provides both platform-as-a-service (PaaS) and infrastructure-as-a-service (IaaS) services and supports many different programming languages, tools and frameworks, including both Microsoft-specific and third-party software and systems. Cloud Services is a PaaS environment and can be used to create scalable applications and services; there are specific software development kits (SDKs) provided by Microsoft for Python, Java, Node.js and .NET. Azure also has file and storage services, data management, analytics and DNS services.