How a GSMME migration works
You can migrate your users' email, calendar, and contact data from a Microsoft® Exchange server using G Suite Migration for Microsoft Exchange (GSMME). If you use an IMAP server, such as Novell® GroupWise® to route mail, you can also use GSMME to migrate email from the server to your G Suite account.
Exchange migrationsWhat's migrated?
You can migrate email, calendar, and contact data from Exchange.
GSMME connects to Exchange and uploads the data to G Suite using the Gmail API.
When you set up GSMME, you enter the Exchange administrator credentials. You also provide a comma-separated values (CSV) file that specifies the Exchange username and the corresponding G Suite username. During a migration, GSMME connects to Exchange and transfers the data to G Suite using the information in the CSV file.
GSMME translates the email message from MAPI to MIME (another email protocol) using Microsoft Outlook®. Any machine running an Exchange migration must have Outlook installed to enable this process.
Note: You can use GSMME if you're using a hosted Exchange environment. However, the way you set up your administrator profile is a little different. For details, see Does GSMME work in a hosted Exchange environment?
The first time GSMME migrates a message or personal storage table (PST) file, it writes a custom property at the root of the message store. After a message is migrated, the same custom property is also written on the message object. If you run another migration, GSMME compares the properties. If they match, GSMME bypasses the message because it’s already been migrated.
If instead you choose to migrate all data, a new property is generated and written to the root of the message store. Since the new property doesn't match the value on an existing message, all messages are migrated, including those previously migrated.
IMAP migrationsWhat's migrated?
You can only migrate email from IMAP servers.
GSMME connects to the IMAP server and accesses email using the IMAP protocol. Then, GSMME uploads mail to the G Suite mailbox using the Gmail API.
When you configure GSMME, you specify the host name and IP address of your IMAP server. You also provide a CSV file that specifies the usernames you want to migrate. During a migration, GSMME connects to the IMAP server and signs in to the user accounts using the information from the CSV file.
When a message is retrieved, GSMME uses the Gmail API to upload the message to the G Suite mailbox.
When data is migrated, its migration status is stored locally in a SQLite database. If you run a migration again on the same machine, the database helps GSMME bypass any data previously migrated.
IMAP versus Exchange migrations
If you use GSMME to migrate from an IMAP server, only email messages are migrated, whereas from Exchange, GSMME migrates email, calendar, and contact data.
The other main difference between IMAP and Exchange migrations is the way the servers retrieve data:
- IMAP migrations connect to source servers and retrieve email data through IMAP.
- Exchange migrations connect to Exchange servers and use local Outlook functions to retrieve email, calendar, and contact data.
Although IMAP and Exchange migrations retrieve data using different processes, they both upload the data using the Gmail API.