Migration from IMAP source to Exchange 2019/2016/2013
I. Pre-migration activities
Below you will find the list of key points to be considered:
Step 1: Prepare a clean target Exchange environment in a new Active Directory forest
The following points need to be revised:
- Send/receive connectors (Exchange 2019)
- Accepted domains (Exchange 2019)
- Default email address policy (Exchange 2019)
- External URLs (Exchange 2019)
- Internal URLs (Exchange 2019)
- Server's certificates (Exchange 2019)
Learn more about the above in Exchange 2016 and Exchange 2013.
Step 2: Prepare domain accounts on the target server
- Create mailboxes in the target environment manually.
- During the mailboxes matching step, you can also set the program to create the mailboxes and the corresponding users automatically.
Please be aware that prior to migration you have to prepare (in the target environment) a mailbox-enabled user account for each user included in the migration.
What is more, if you choose either to manually create the mailboxes or allow the program to prepare them for you, be advised that the account data (such as permissions) will not be migrated.
If you have already created new mailboxes on your target Exchange Server, it is possible to hide them from the GAL (e.g. to prevent your users from sending emails to them until the migration is finished). These mailboxes will be still visible in CodeTwo Exchange Migration and the migration will proceed as usual.
Step 3: Verify the configuration and rights of the admin account that will be used to connect to the target Exchange server
Make sure that the target admin account is assigned the necessary management roles and that this account is mailbox-enabled.
Verify the following:
- Check if the target admin account has the following roles assigned:
- View-Only Recipients
- View-Only Configuration
- Public Folders*
- Mail Recipient Creation*
- Mail Recipients*
Please note that the Public Folders role is only required if you plan to migrate public folders. Moreover, the Mail Recipient Creation and Mail Recipients roles are required to create new users and mailboxes. Therefore, it's not required to assign them to the admin account if you are migrating data to the mailboxes that already exist on the target server.
- check which roles are assigned to a specific user. To do that, run the Exchange Management Shell on the target server and enter the following cmdlet: Get-ManagementRoleAssignment -RoleAssignee “UserName”, where instead of UserName you need to enter a valid Name or Alias of your mailbox-enabled AD user; or
- check which users are assigned a specific role. To do that, run the Exchange Management Shell on the target server and enter the following cmdlet: Get-ManagementRoleAssignment –Role “RoleName”, where instead of RoleName you need to enter a specific role, e.g. ApplicationImpersonation.
- Access to the target server's EWS service using IP or Domain Name, e.g. https://[Exchange_IP]/EWS/Exchange.asmx or https://[Exchange_Name]/EWS/Exchange.asmx
- To connect to EWS from the outside of the local network you need to have the external EWS URL correctly configured:
- Open the Exchange Management Shell on the target server and check if the ExternalUrl is defined: Get-WebServicesVirtualDirectory | fl
- If there's no address in the ExternalUrl line it needs to be defined. Execute the following script: Get-WebServicesVirtualDirectory | Set-WebServicesVirtualDirectory -ExternalUrl https://[Target server's internet name]/EWS/Exchange.asmx
Step 4: Adjust the EWS throttling settings and change the maximum size limit of sent mail to decrease the time of migration processing
- To speed up the migration process, change throttling settings on target Exchange by following this Knowledge Base article.
- To allow migration of big items, change message size limits on target Exchange by following this Knowledge Base article.
Step 5: Prepare source IMAP server settings
Verify the following:
- You have a list of all credentials for mailboxes you want to migrate via IMAP - here is why
- Know your IMAP server address or IP, port and SSL connection support - for example, for Gmail those are: imap.gmail.com, port 993, enabled SSL
- IMAP access is enabled on the source server - see here how to do this for Gmail and Google Workspace (formerly G Suite)
Step 6: Install and activate CodeTwo Exchange Migration
When migrating data from an IMAP server, the program can be installed anywhere, e.g. on a workstation outside source and target domains. However, it will most likely work best if installed directly on the target Exchange Server.
The following additional components will also be installed, as they are required for CodeTwo Exchange Migration to run properly:
- .NET Framework 4.6.1 or higher (required on all systems),
- Windows PowerShell 3.0 (required on all systems).
The installation wizard will guide you through the whole installation process. After the installation is finished, remember to activate the program.
II. Migration process
Step 1: Connect to the source server
Make sure that the software user who runs the migration is a local administrator.
When you start the program, you will see the Dashboard view. Click Create a new migration job link on the How to start card. Select the source server type: IMAP. The create IMAP migration job wizard will open. Set the name of the job and click Next to proceed to the Source mailboxes step. If this is your first migration job, you will need to configure the connection to the source IMAP server. Click Add new source connection and a wizard will open. You need to go through these steps:
- Server connection - in this step, you need to choose your IMAP source and some connection settings.
- Throttling - there you can customize the software behavior if you stumble upon throttling issues on the IMAP source server.
- Configuration - this process configures your connection based on the settings provided in the previous steps.
Step 2: Continue the job configuration to provide source mailboxes credentials
After successfully configuring the source connection, you will get back to the Source mailboxes step of the migration job wizard. Now you need to define which mailboxes you want to migrate.
- Prepare a CSV file that contains source mailbox credentials as listed below. Do not worry that much about the CSV format. The CSV import feature lets you adjust the software to the file format used, i.e. you do not need to use a specific fields delimiter - use the one you like, you will be asked by the CSV import feature what kind of delimiter was used in the file.
- Login - required
- Password* - required
- First Name - optional
- Last Name - optional
- Display Name - optional
- Click Import from CSV and select your CSV file.
- Configure the software to properly import data from your CSV file.
* Or app password, if you are migrating from Google (Gmail or Google Workspace). Learn more
Step 3: Set the target connection
After successfully configuring the source connection and choosing source mailboxes, click Next to configure the target server connection. In the Target mailboxes step, select Add new target connection from the Target server drop-down menu. A simple wizard will open.
- In the Server connection step, choose either Autodiscover Exchange Server (default option) to automatically find the proper target server or configure the connection manually.
If you decided to configure the target connection manually, be aware that using an IP address will make granting impersonation rights and creating mailboxes impossible unless you configure PowerShell Virtual Directory in IIS to allow basic authentication.
- Admin account – provide a valid UPN and password of the account that will access the target server (remember that the admin account must fulfill the requirements specified in I Pre-migration activities, Step 3). Click Next to move on to the Configuration step.
UPN (User Principal Name) is the name of a system user in an email address format. Learn more.
- Configuration – this process configures the target Exchange server connection and checks whether the account provided in the previous step has the necessary roles assigned. If not, the program will attempt to assign them automatically. In such a case, you might be asked to provide the credentials of another account that belongs to the Organization Management role group. This account will not be used to connect to the target server, but only to assign the missing roles.
Once the configuration ends successfully, you will see green check marks. If any errors appear, see Troubleshooting.
After your connection is established, click Finish. You will return to the IMAP job configuration wizard.
Step 4: Match source and target mailboxes
Matching the source mailboxes with the target mailboxes can be done automatically, by using the built-in automatch feature, or manually. We suggest that you start off by matching mailboxes automatically and modify the automatch settings if not all the mailboxes were matched in the first run. Use the manual option only if there are any mailboxes left unmatched after several automatch runs with a different configuration of the automatch mechanism.
To match mailboxes automatically, click the Match mailboxes button. In the window that opens, click Automatch > Automatch all mailboxes or select the mailboxes you want to match and click Automatch > Automatch selected mailboxes. Configure the automatching mechanism and click Automatch to start the matching process. If not all the mailboxes were matched, modify the automatch mechanism and run it again. Repeat this as many times as necessary.
Read more about the default configuration of the automatch mechanism and how to customize it
If any source mailbox is left unmatched despite several attempts to match it automatically with different automatch settings, match it manually.
Note that you can set the program to create target users and mailboxes on your Exchange server, whether you’re matching mailboxes manually or automatically. Learn more
When you have matched all your mailboxes, save your configuration and close the matching window. Continue with the migration job wizard. The next steps will allow you to configure additional options.
Step 5: Customize all necessary aspects of the migration job
You can configure the following additional options:
- Scheduler - allows you to set the job to be automatically started in the desired time periods, so you do not have to control it manually.
- Time filter - is used to exclude items that are older or newer than a particular date
- Folder filter - may completely exclude specific folders from the migration process
- Advanced settings - provides an option to define how many mailboxes should be migrated at the same time. This number should correspond to the number of logical processors. You can also define the maximum size of items to be migrated.
Step 6: Start the migration
Move on to the JOBS tab and click Start on the toolbar to begin the migration.
The migration processing time depends on several different factors, e.g. the number of mailboxes and items, the speed of internet connection, EWS throttling settings. We have published more details here.
Step 7: Check if the number of migrated items in the target mailboxes matches the source server mailboxes
If you notice any missing items in the Target mailbox, restart the migration by using the Run delta migration option.
Please be aware that the program does not migrate some specific folders at all. Those are i.e. Sync Issues or ones created while putting a mailbox on litigation hold.
If any problems appear during the migration process, they will be indicated on the dashboard, pointed out in the reports and logged in the log files. Check out the software's diagnostics.
Step 8: Check if there are any new items in the source mailbox after migration
Once the migration is finished and you have noticed that some new items appeared in the migrated source mailbox, just restart the migration by using the Run delta migration option. Please keep in mind that this feature migrates only new items, not the modified ones. Delta migration can also be used to resolve issues with any items that failed to migrate on the first attempt.
III. Post-migration cleanup
Step 1: Change DNS records (MX, Autodiscover)
You need to change MX records to enable mail flow to new servers. Additionally, you should also set up Autodiscover record to facilitate connecting migrated mailboxes with a mail client (e.g. Outlook). Detailed information on how to do so on Exchange Server 2019 and 2016 can be found in this Microsoft article. Please note that this process may take several hours.
If any new items appear in a source mailbox while the MX records are being changed, it is possible to migrate these items after the records migration process is completed. It can be done by using the Run delta migration option.
Step 2: (Optional) Disconnect domain
To avoid possible DNS conflicts, it would be a good idea to disconnect your domain name from the source IMAP server. Consult your domain name registrar in you need more information on how to do so.
For additional resources, refer to Frequently Asked Questions or contact us.