Office 365 Email Migration Options

This is not meant to be an exhaustive, how-to post… just more of a run through of the different strategies available for migrating to Office 365 from various email platforms, and my experiences with them.

1. Exchange to Office 365

This is the smoothest method available – if you have Exchange 2007 or later,* Office 365 will auto-detect your settings and migrate your mailboxes to the cloud with minimal fuss. And (even better), this also grabs your distribution groups and email aliases on your mailboxes! Definitely my favourite way to go if I have access to an on-premise Exchange server to migrate from.

* Exchange 2003 requires manual setup, and is a little tricker to set up – but once you have your connection, works just as well as the newer versions.

2. IMAP Migration

IMAP Migration is what you’d use if you were going from another hosted provider – whether they be Google Mail, or even another hosted Exchange. This method of migration has several drawbacks, and is my second least favourite method of migrating mailboxes into Office 365.


  • These drawbacks include:
    • IMAP migration will only grab the inbox and Mail enabled folders – it will not pick up your calendars or contacts, so you’ll need to manually export those to a CSV or ICAL file.
    • Requires setting up a CSV file with email addresses and credentials for all the mailboxes to be imported – there is no intelligence to find your mailboxes and distribution groups.
    • Migration control is funky – once you’ve started a migration, it needs to run a full pass at all the mailboxes before it will start over and rescan the mailboxes. This means that if you’ve found errors (of which there will be plenty), fixed them and then re-ran your migration, it simply picks up where it left off – it doesn’t go back over and rescan your mailboxes for changes.
    • It takes a long time – a small migration of around 35 users ran for almost two weeks on its initial scan without ever completing its initial pass. By the time we were ready to cut over MX records and go live, we still needed to manually export and import mailboxes.
    • As I’ve mentioned before, there is no graceful way to stop the migration – deleting the migration batch will not run a final sync… very frustrating!

    And a couple of gotchas:

    • Won’t copy any folders with a forward slash (/) in its name.
    • Won’t copy any items larger than 35MB, and it won’t tell you what it’s skipped… it’s just a fun mystery for you to explore!


3. PST Capture

Microsoft provides a free PST import utility called PST Capture – and while it sounds like a great idea, especially in an environment where you have a lot of PSTs to upload, it is not without its own batch of headaches.

First, you need to install the PST Capture Console on a host computer – then, you install a PST Capture Agent on all the computers that you want to be able to scan for PSTs. Once you have these two components in place, the agents will report back to the console with all the PSTs that they’ve found that need to be imported. Oh, and did I mention that you need to have a copy of 64-bit Outlook installed? 32 bits need not apply!

In my experience with this tool, I found it very unreliable – even after jumping through all the required hoops to have it working on your network, it would fail on every attempt to upload a PST into Office 365. Overall, a lot more frustration then there needs to be… which brings me to my tried and true, “if all else fails do this” option.

4. PST Export /Import

If you do not have the ability to migrate from an on-premise, Exchange 2007 or greater server, this is THE ONLY OPTION I would consider. Mind you, it’s not completely automated, and it requires you to set up users, aliases and distribution groups beforehand. However, it just works! All you need to do with this procedure is walk up to each desk, export their Outlook profile to PST (which catches mail, calendar, tasks, and contacts). Once you have a PST sitting on their PC, create a new profile that connects to Office 365 and import that PST. Once you’ve started importing the PST, you can move on to the next computer and repeat the process.

The beauty of this procedure is that you don’t need to worry about when it gets up into the cloud – it might take a while to get all the information uploaded, but your user is working in the meantime, and all their data is at their fingertips. You even have the ability then to import their autocomplete data, earning their undying affection and names like “Superhero” and “Rock star” 😀

TL;DR? My final suggestions are simple – if you have the option to do a clean migration from Exchange 2007 or newer… do it. It works well, and is (mostly) stress free. If you have any other scenario, export mailboxes manually to PST and import them into clean Office 365 profiles. You’ll be glad you did.

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