Email Migration

Email migration is the process of moving your existing mailbox content to Office 365 and Exchange Online. Migration can occur as quickly or as slowly as your organization wants. Small organizations may be able to migrate mailbox content to Exchange Online overnight or over a weekend. Larger or more complex organizations typically prefer to establish email and directory coexistence for a longer period of time and perform a controlled migration in logical stages. The ultimate goal of the migration process is to have a unified migration experience for end users with minimal impact to their daily routines.

Office 365 for enterprises supports five types of mailbox migrations:

 Exchange Server mailbox migrations

 Hosted Exchange mailbox migrations

 IMAP4 mailbox migrations

 Lotus Notes mailbox migrations

 Novell GroupWise mailbox migrations

Each type of mailbox migration is briefly discussed below.

3.8.2.1 Exchange Server Migrations

If your organization is using Exchange Sever 2010, Exchange Server 2007, Exchange Server 2003, or Hosted Exchange, you have several ways to migrate mailbox data. Table 12 describes them.

The Microsoft Office 365 Deployment Guide for Enterprises is primarily focused on mailbox migrations for Exchange hybrid deployments.

Table 12. Types of Exchange Server Migrations

Type Description Tools/Methods

Simple Exchange Migration (Cutover Migration)

Intended for small organizations that desire a quick cutover, with no coexistence, from their existing Exchange mail environment to Exchange Online. All on-premises mailboxes are migrated in preparation for moving your entire email organization to Exchange Online. You can migrate a maximum of 1,000 mailboxes from your on-premises Exchange organization to Exchange Online.

User identities are automatically provisioned by the tool. After cutover, identity federation may be deployed.

Email Migration tool via the Exchange Control Panel.

For step-by-step instructions, see Migrate All Exchange Mailboxes to the Cloud.

Type Description Tools/Methods Staged Exchange

Migration

Intended for organizations that desire a shorter period of coexistence from their existing Exchange mail environment to Exchange Online. User identities will automatically be provisioned by the Directory Synchronization Tool. After all users are migrated to Exchange Online, identity federation may be deployed.

This type of migration allows you to maintain coexistence between your on-premises and Office 365 email organizations.

In this scenario, you can move some mailboxes to Exchange Online while

maintaining the rest of the mailboxes in your on-premises mail environment.

Email Migration tool via the Exchange Control Panel and a CSV file; Directory

Synchronization Tool (DirSync) to keep your on-premises Active Directory synchronized with Office 365 and Exchange Online.

For step-by-step instructions, see Migrate a Subset of Exchange Mailboxes to the Cloud with a Staged Migration.

Note: On-premises Exchange decommissioning after a staged migration should be planned carefully with the help of an Office 365 deployment specialist.

This type of migration enables on-premises users can see calendar or free/busy

information for Exchange Online users. You must add a hybrid server to your on-premises Exchange environment.

Note: The migration velocity, especially if any third-party tools are involved, may be impacted by the Exchange Web Services (EWS) limits for Exchange Online. For more information, see the blog entry Exchange Online Throttling and Limits FAQ.

3.8.2.1.1 Hybrid Reverse Proxy Configuration

The Exchange Mailbox Replication Proxy (MRSProxy) service may not work properly if a reverse proxy, such as Microsoft ISA Server or Microsoft Forefront Threat Management Gateway(TMG), is publishing Exchange services in the perimeter network and requires pre-authentication. You should perform the following steps if this is your scenario:

1. Create an additional ISA/TMG rule that uses the same listener as the original Exchange 2010 rule that already allows pre-authenticated traffic to the internal Exchange server(s).

2. Configure the new rule as follows:

 Authentication Delegation: No delegation, but client may authenticate directly.

 Users: All Users

 Paths:

o /ews/mrsproxy.svc

o /ews/exchange.asmx/wssecurity

o /autodiscover/autodiscover.svc/wssecurity o /autodiscover/autodiscover.svc

 Rule Priority: This rule must be set to a higher priority than the other Exchange publishing rules.

3.8.2.2 IMAP Migration

An IMAP migration is used by small organizations that desire a quick cutover, with no

coexistence, to Exchange Online services from their existing mail environment by leveraging the IMAP protocol. User identities are automatically provisioned with the IMAP migration tool within the Exchange Control Panel. Note that you will need to create Exchange Online mailboxes before beginning this process. See the Help topic Migrate E-Mail from an IMAP Server to Cloud-based Mailboxes for more information. After cutover, identity federation may be deployed.

You can use the Email Migration tool in the Exchange Control Panel and a CSV file to migrate the contents of users' mailboxes from an IMAP messaging system to their Exchange Online mailbox. Supported IMAP servers include the following:

 Courier-IMAP

 Cyrus

 Dovecot

 UW-IMAP

 Exchange 2010

 Exchange 2007

 Exchange 2003

During the migration, to avoid overusing the remote server’s resources and bandwidth, Exchange Online creates fewer than 10 connections to the IMAP server.

3.8.2.3 Lotus Notes and Novell GroupWise Migrations

If your organization is migrating to Exchange Online from a non-Microsoft platform such as Lotus Notes and Novell GroupWise, you may want to evaluate migration solutions offered by consulting services and third party software providers.

The Recommended Deployment Partners area of the Microsoft Online Services deployment site can help you find technology consultants and partners with expertise in Office 365 migration services and solutions.

3.8.2.4 Reducing Mailbox Size

The size of a mailbox, along with available bandwidth to the Internet, is a limiting factor in achieving a high migration velocity.

A common practice to reduce the size of the mailbox is to move mail items out of the mailbox to an archive (for example, a .PST file) either manually or with auto archive functionality. This practice is discouraged because when the user moves the mail items back to the new Exchange Online mailbox after migration, the Exchange Online mailbox will not allow the user to reply to the mail.

When attempting to reduce mailbox size, consider doing the following:

 Delete or archive mail in the Sent Items folder

 Delete or archive all Calendar attachments

 Delete or archive Calendar items over 30 days old

 Delete or archive Inbox items over 90 days old

 Search for and delete attachments over 5 MB

 Disable Journaling

 Empty the Deleted Items folder

 Enable AutoArchive via Group Policy

 Run the Mailbox Cleanup wizard from the Outlook Tools menu (Outlook only)

Note: The number of days and file sizes are recommendations only. They may not be suitable for your organization.

3.8.2.4.1 Mailbox Assessments

Your organization will need to assess the number of mailboxes, mailbox size, and the rate of mailbox size growth in your existing environment. This information will help you evaluate the

impact of migration traffic on your network, which must be considered when scheduling migrations.

If your organization enforces maximum mailbox size limits, this information is also important to consider when you define Exchange Online storage capacities. Your new Exchange Online environment should let all users store the same amount of data or more in their Exchange Online mailboxes. It may be necessary for users with extra-large mailboxes to move some of that content from their mailboxes to some form of offline storage, such as a Microsoft Office Outlook .PST file to facilitate timely mailbox migrations.

In addition, when evaluating your existing mailbox inventory be aware that your organization receives 25 GB of mailbox space for each Exchange Online (Plan 1) and Exchange Online (Plan 2) user license purchased. Each Exchange Online Kiosk user receives 500 MB of mailbox storage. Administrators can use Remote PowerShell to reduce maximum mailbox sizes for some or all of their users.