True, hybrid does require more up-front configuration, and of course there are those pesky pre-requisite requirements of having Exchange 2010 or 2013, as well as Azure AD Connect for Directory Synchronization. But the benefits do outweigh these concerns—trust me. The overall time commitment to your migration project will plummet with a hybrid server, and it will be easier.
But what if you are still on Exchange 2003 or 2007? Aren’t you pigeon-holed into one of the other migration methods by default? Absolutely not; for example, if you install a 2013 server alongside 2007, you are covered. Microsoft allows you to do this with a free license if you have a qualifying Enterprise Office 365 plan, and you intend to use a hybrid deployment to move to Office 365!
The migration checklist goes something like this:
- Ensure all your domains are verified in your Office 365 tenancy;
- Your on-premises Exchange environment should be fully patched/updated;
- Active Directory users’ UPN names should be configured to match their email address (e.g. they should not look like firstname.lastname@example.org, but email@example.com)
- You must install and configure Azure AD Connect (formerly DirSync);
- This step is only required if you do not already have Exchange 2010, 2013:
- Re-key & reimport your UCC cert to include a new DNS name such as “hybrid.domain.com” in addition to mail, autodiscover, etc.;
- Get your hybrid Exchange product key
- Install a new or temporary Exchange 2013 server with all of the standard roles, activate using the key, and import the UCC cert;
- Ensure your firewall is configured to allow HTTP/HTTPS and SMTP traffic to/from the new Exchange server, same as it is configured for the old Exchange server;
- Create a new DNS (A) record for hybrid.domain.com—for the new server—and point autodiscover CNAME records to hybrid.domain.com;
- Run the Hybrid configuration wizard from the Exchange server;
- Migrate mailboxes using the Remote Move method;
- Migrate Public Folders, if required;
- Complete the Office 365 setup by finalizing migration batches and cutting-over DNS records:
- Autodiscover CNAME and SCP should be configured to point to the hybrid server;
- If you want mail to flow into Office 365 directly instead of coming through your local Exchange server, be sure to update MX and SPF to point to Office 365 also (recommended).
- Remove legacy Exchange servers and update on-premises DNS (only if necessary, depending on your scenario).
That is really all there is to it—notice that it doesn’t require super specialized skills or an Enterprise-sized organization. If you can run through a couple of wizards, import a certificate and change some DNS records, you will be able to do this migration all by yourself, and with minimal time commitment/end-user hassles.
If you do not want to keep your hybrid server around after the fact, then there is an approved process to remove it. Please note that certain management features are easier with a hybrid server in place, and I generally recommend keeping one around if you are planning to continue using password/directory synchronization. Microsoft also recommends this. More on this topic here.