Migrate your mailboxes to Office 365


適用版本: Office 365

上次修改主題的時間: 2014-09-30

As part of the process of deploying Office 365, you can choose to migrate the contents of user mailboxes from your source email system to Office 365 mailboxes. We recommend that you migrate mailboxes by using Internet Message Access Protocol (IMAP) when:

  • Your source email system supports IMAP.

  • You have more than 50 mailboxes.



Setting up email for your users is a required step in a setup path for Office 365. For more information, see 簡化您的 Office 365 部署.

Here are a few limitations to be aware of:

  • Only items in a user's inbox or other mail folders can be migrated. This type of migration doesn’t migrate contacts, calendar items, or tasks.

  • You can migrate a maximum of 500,000 items from a user’s mailbox (emails are migrated from newest to oldest).

  • The biggest email you can migrate is 35 MB.

  • If you limited the connections to your source email system, it’s a good idea to increase them to improve migration performance. Common connection limits include client/server total connections, per-user connections, and IP address connections on either the server or the firewall. If you haven’t limited these connections, you can skip this task.

To migrate email, you need access to the user mailboxes in your source email system. If you know the user passwords, or you can access their mailboxes by using administrator credentials, there won’t be impact to users until you shut down your source email system.

If you can’t access user mailboxes yourself, you’ll have to reset the passwords. This lets you to access the user mailboxes by using a new password that you know. If users don’t know the new passwords, they won’t be able to access their old mailboxes during or after the email migration. You can distribute the new passwords after the migration if you want users to have access to their old mailboxes.

To finish an email migration successfully, it’s a good idea to be comfortable doing these tasks:

  • You create a list of mailboxes to migrate in Excel. You add your users’ email addresses, user names, and passwords to this file.

  • You use step-by-step wizards in Office 365 to configure and start the migration process.

  • You change your organization's MX record to point to Office 365 when the migration is complete. Your MX record is how other mail systems find the location of your email system. Changing your MX record allows other mail systems to begin to send email directly to the new mailboxes in Office 365. We provide instructions on how to do this for many DNS providers.

  • If you’re migrating mailboxes from Exchange 2003, you need a couple of additional skills:

    • You have to use the command prompt to complete several of the tasks. We provide the exact syntax to type.

    • You have to purchase a digital certificate from a trusted third-party certificate authority (CA), if you don’t have one already. Digital certificates are an important part of helping secure the communication between the on-premises Exchange servers and Office 365 during mailbox migration. We provide instructions on how to install the certificate to Exchange 2003.

If you’re comfortable with what’s involved in migrating mailboxes to Office 365, you’re ready to get started.



Get started

The first step is to answer a question that helps us provide the migration steps for you. Which email system are you using?

There are other ways to get users up and running with Office 365 email without doing these tasks.


Method Description More information

Start using new mailboxes and don’t migrate existing email

This is the fastest and easiest way to get started with email in Office 365. Users can start sending and receiving emails in their new Office 365 mailboxes, which were automatically created when you created the user accounts.


Use a third-party email migration tool

Migration tools can help speed up and simplify email migration. You can find a list of tools in the Office 365 Marketplace.

Outlook 圖示

Use Outlook to move information between email accounts

This is a three-step process that is performed one mailbox at a time. Here are the steps:

  1. Add the source email account as an account in a desktop version of Outlook.

  2. Export all of the information from that account to an Outlook data file (.pst file).

  3. Import that Outlook Data File into an Office 365 account.

You can do this process yourself for each user mailbox, but this can take a long time if you have a lot of mailboxes. Another option is to teach users how to do this themselves. To learn how, see Use Outlook to move information between email accounts.


Hire a partner to help migrate your email

You can find a list of partners in the Office 365 Marketplace.