Bulk Mailbox Migration to Office 365

Aftab Alam    Aftab Alam     Updated On - 24 Jan 2019

Due to the Advent of efficient cloud platforms and their efficient services, many business owners want to move their Exchange mailbox to Office 365. The size of exchange mailbox is generally quite heavy, and it can be a time consuming and error-prone task to perform a complete migration. There are some methods which can help you in completing the desired tasks-

Method 1- Use CSV file –

A CSV file is completely suitable for bulk migration of large mailboxes to Office 365. You can use a CSV file while using the Exchange admin center (EAC) or the New-MigraitonBatch cmdlet in Exchange Management Shell to create a migration batch. There are following migration scenario where a CSV file is useful –

  • Onboarding remote move migration –
    Onboarding remote move migration helps you to migrate mailboxes from on-premises Exchange online to Office 365. It works in the Exchange hybrid deployment scenario.
  • Offboarding remote move migration –
    Offboarding remote move migration is opposite to onboarding remote move migration; here you can migrate Office 365 mailboxes to your on-premises Exchange environment.
  • Staged Exchange migration –
    In staged Exchange migration, you can migrate a subset of mailboxes from an on-premise Exchange organization to Office 365.
  • IMAP migration –
    In this type of migration, you can migrate mailbox data from an IMAP server (including Exchange server) to Office 365.

How to use CSV file for bulk mailbox migration?

The CSV file has a defined format under you can insert the required mailbox information. The first row (header row) lists the names of attributes, or fields, specified on the rows downwards. Each attribute is separated by a comma. Each row under the header row represents a user and provides complete information required for migration. The attributes in the row must follow the same order as the attributes names in the header row. Finally, you can create a CSV file in any text editor, but it is better to create in Microsoft Excel Spreadsheet page as it can make easier to insert attribute in the dedicated cells. Always save the file in .csv or .txt format.

NOTE – If the attribute value for a record is null, then don’t type anything for that attribute. But, you should enter the comma to separate the null value from the next attribute.

The following section will describe you what attributes you should enter for different methods of migration –

  • Staged Exchange Migration –
    Attribute – EmailAddress, Password, ForceChangePassword.
  • IMAP migrations –
    Attribute – EmailAddress, UserName, Password.

Method 2- Cutover migration –

Cutover migration is suitable in such situations when the number of mailboxes in Exchange Account is lesser than 2000. Here is a brief procedure of cutover migration conducted by Exchange Administrator –

  1. Exchange Administrator briefs all users about upcoming changes and verifies the domain ownership.
  2. Create empty mail-enabled security groups in Office 365.
  3. Connect Office 365 to the on-premises email system.
  4. Migrate the mailbox and verifies the process.
  5. Grant access rights to the users.
  6. Configure the domain to begin routing email to Office 365 directly.
  7. Verify the routing has changed, and then delete the cutover migration batch.
  8. Complete post-migration tasks in Office 365 like creating and assigning a new license to the user), domain name system (DNS).
  9. Send a welcome letter to all the users and provide complete information that how they can log in to their accounts.

Method 3- Hybrid migration –

The hybrid migration is done when you have to maintain both on-premises exchange and online Exchange. This can be done when:

  • You are using either Exchange 2010 or 2013
  • You want to migrate in small batches

PST to Office 365 migration –

Using this method, you can first convert the Exchange database file (.EDB) to PST format and later import the PST files to Office 365. There are multiple third-party applications which can either convert EDB to PST or import PST to Office 365, but there is one tool Kernel import PST to Office 365 which can migrate an unlimited number of mailboxes from on-premise and hosted exchange to Office 365. Import PST to Office 365 tool does not require any prior preparation and fully migrates mailboxes including the desired items and provides a full report after successful migration.