Migrating from Exchange to Office 365 - Part 1 - IMAP


In this Tech Tip series, I’m going to talk about using Office 365′s built-in migration tools to move your mailbox data from on-prem Exchange to the cloud. There are several third-party options available that give you a little more granular control over the process, but the native tools actually work pretty darn good… and they’re free!

This first post will cover the specifics of using one of the four available migration options: IMAP migration. This is not the “best” or fastest option by any means, but if you’re working with an [older] Exchange environment that for some reason doesn’t have RPC or Outlook Anywhere exposed, IMAP is an easy hole to punch in a firewall. (Port 143 if using standard IMAP, port 993 if using IMAP over SSL.) You can verify that 143 is open by testing its public URL or IP with Telnet.


Alternatively, you can also use the IMAP option with the Exchange Connectivity Tester.

Once you’ve verified that IMAP is exposed and working, log into the Microsoft Online Portal with administrator credentials and open the Exchange Admin Center.


Once you’re in the EAC, click the Migration link.


Now click the plus sign (+), and choose the option to Migrate to Exchange Online.


On the screen that pops up, choose the IMAP migration option and click Next.


Now - one of the things about IMAP migrations is that the “user pool” is defined by a CSV file. What this means is that any and all of the users that you want 365 to migrate out of your Exchange box have to be defined in a CSV file. It’s simple enough, the CSV file only requires 3 columns (EmailAddress, UserName, Password) and you would populate each row with the data for each user you want to move. This works for a multitude of users or even a single user. Create this file in Excel, save it to your desktop, and then upload it to 365. For example:



On the following screen you’ll need to input the information for your Exchange server. (On this particular server that I’m using for this example, it’s not running an internal CA nor was it secured with a third-party cert, so the encryption is set to None.)


Click Next, give the batch a name, click Next again, and then enter the email address of the person you want to receive the completion report. You must enter an email address here - but it’s important to note you CAN specify an address not inside of the 365 organization. You must also choose whether or not to start the batch automatically or not. Then click New.



If you chose to start the batch manually, you can then highlight it back on the Migration screen and press the ‘Play’ button. One of the things that I’ve noticed is that these batches don’t always start right away. You may end up waiting a few minutes before you start seeing it move items. Depending on the internet connection of the source Exchange server, as well as its overall condition, health, and size of the mailboxes you’re moving, this process could take minutes, hours, or even days.

It’s time to throw a retirement party for Exchange 2003!


Exchange Server 2003 came into this world on September 28, 2003. It brought with it a host of new features, including improved migration tools to ease the transition from older versions of Exchange, enhanced heuristic message filtering to help direct spam into the Junk folder, and, if you had Service Pack 2 installed, a database size limit of 75 gigabytes. This was unimaginably large for the time.

That was eight years and eleven months ago. In that time, we have also seen Exchange Server 2007 and Exchange Server 2010 come into the mix as well. If your organization is still running Exchange Server 2003, here are some reasons why it is time to upgrade.

  1. Microsoft created a handy chart to break down the differences between Exchange Server versions.
  2. Modern desktop mail clients like Outlook 2010, Outlook for Mac 2011, and Apple Mail all require Exchange Server 2007 or later, and they won’t talk to Exchange Server 2003 at all. So if you get a new Windows machine with the latest version of Office or one of those shiny new Macs, those users will be stuck using Outlook Web Access webmail to access email, calendars, and contacts.
  3. Outlook Web Access on Exchange Server 2003 forces browsers other than Internet Explorer to use “Light” mode, which just means that many of the features and options beyond simple sending and receiving email are disabled or invisible to anyone running a different browser (such as Firefox, Chrome, or anyone on a shiny new Mac).
  4. The 75 gigabyte size limit I mentioned before applies only to Exchange Server 2003 Standard, but there is a lot more email being sent today than there was 9 years ago. It does not take very many users with large mailboxes to hit that size limit, and when you do Exchange Server 2003 will shut itself off to prevent database corruption or data loss. That means no more email until the size of the database is reduced. The newer versions of Exchange Server do not have this limitation.
  5. If the software package is nearly 9 years old, chances are that the hardware running it is on its last legs too. While it might be running just fine, it is most likely out of warranty and may even be in End Of Life status, making replacement parts hard to find, making disaster recover more difficult, and increasing costs and downtime.
  6. The prospect of replacing an Exchange server can be a daunting one, costing many thousands of dollars. One way to avoid this expense and to simplify your office network is migrating to a hosted Exchange system in the cloud instead. By getting rid of your old office server, your business can keep running if there is an internet service failure or power outage in your building. Take a look at Everon’s own cloud email and business continuity solutions.
If you are considering retiring your old server hardware running Exchange Server 2003, there has never been a better time. And Everon can help you do it. Call us at 888-244-1748 if you have questions about server migrations or our cloud email solutions.