How Long Does an Email Migration Take and What Do I Need?

Migrating your email to Microsoft 365 can feel like a big change and, consequently, the expectation is often that it will take a long time too. Well, does it? The answer is a solid maybe; ultimately there are a variety of factors to consider and things to prepare ahead of the migration.

What Do I Need?

Before committing to migrating, it’s always important to consider your current environment, and what else can or should migrate alongside:

Do you have file servers or other cloud storage that could be consolidated?
Do you rely on any apps which leverage single-sign-on?
Is there anything that you need that isn’t compatible or requires extra steps to migrate?

The very first step for any migration is setting up your Microsoft 365 tenant, specifically ensuring you have active licenses: the licences are what give your users the mailboxes their email is migrated into. Depending on the licences you go with, you’ll also have access to many other services within Microsoft 365 (it isn’t strictly required, but it could be worth deploying a Zero Trust strategy to be as secure as possible before completing the migration.)

Another big factor of an email migration is preparing your end-users for the migration, what to expect, and their responsibilities. If taking the Hybrid route, Outlook will automatically reconfigure itself when a user is migrated, but other devices or mail clients will need to be manually reconfigured, so it’s important to make users aware of what they’ll need to do here. If you’re using a cloud migration approach (as discussed further here), additional considerations need to be made as there are a variety of other factors to consider, most notably how will the migration tool you go with actually get to the data to sync it.

Traditionally, 3rd party migration tools would require each user to provide their email address and password to the tool itself for it to be able to sync their email. The cloud migration tools we use can also set the logins for the new Microsoft 365 accounts through this method. Nowadays, most environments have built-in admin roles that allow all mailboxes to synchronise with only 1 login, rather than everyone’s login. That definitely helps, but this brings up another question; how will the credentials for the new Microsoft 365 be handled? There’s a wide variety of approaches you can take here, whether you create the new accounts yourselves and manage passwords internally, synchronising the accounts and credentials from your on-premises Active Directory, or our migration tools can let users set their own credentials. There are many other paths you can take outside of these options, so whichever method works best for you, we can advise and assist you to roll this out.

Lastly, it’s important to think about how you want your mail routing to work and the requirements there. It may be as simple as having everything flow through Microsoft 365 directly post-migration, but if email currently flows through any 3rd party systems or you plan to implement them as part of the migration, such as spam filters or journaling tools, factoring this into your migration plan is critical. If you take the hybrid approach there are even more options, as you also have the option to route all email through your server, even for migrated users.

How Long Does It Take?

All sorts of factors can impact how long an email migration takes:

How many mailboxes do you need to migrate?
How much data is in each migrating mailbox?
Where are you migrating from, and how much bandwidth can your environment support?
How much intervention is needed from migrating users and how much support will they need post-migration?

Outside of these points and your answers to the above section, the biggest factor is which method you go with: Hybrid or Cloud. Hybrid migrations typically take longer, as they can require more preparation pre-migration start, as well as granting the flexibility to migrate users gradually. Cloud migrations can be much faster, as all users generally need to be migrated in one go due to most of the critical changes such as mail routing impacting all users.

On average, a cloud migration can take roughly 2-3 weeks from the point of starting data migration to fully switching over. This is very much a ballpark figure; a migration with only a few mailboxes and not much else in terms of integration can be much faster, others with a large, international userbase can take longer. It’s best practice to switch over to Microsoft 365 after the data has finished migrating, which naturally leads to the number of users and data being one of the main factors that impact how long a migration can take.

Owen Pridden | Senior Technical Specialist

Originally posted 3rd September 2021

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