How to Migrate Mailboxes to Microsoft 365
Moving email to Microsoft 365 brings better remote access, easier scaling, and reduced on-premises maintenance overhead. The migration itself is not one-size-fits-all: there are several paths to get a mailbox across, and selecting an unsuitable method can increase cutover time, administrative effort, and migration risk. This guide covers the common migration paths so the right one can be chosen before work begins in the admin center.
Migration Method Types
Each migration method suits specific scenarios; see the Office 365 migration methods guide for a full comparison. The Office 365 migration tool from EdbMails brings these approaches together in a single platform.
Cutover migration
All mailboxes move to Microsoft 365 in a single scheduled window. This method works best for smaller organizations that can complete the move within a single cutover period; larger mailbox counts are generally better suited to staged or hybrid migration instead.
Staged migration
Mailboxes move in batches over a longer period, which suits larger mailbox counts on legacy on-premises Exchange environments. Each batch is migrated and validated before the next begins, reducing the risk concentrated in a single large cutover event.
See Microsoft's staged migration documentation.
Hybrid migration
Hybrid migration connects an on-premises Exchange environment to Microsoft 365 so mailboxes can coexist across both environments and move gradually rather than in a single batch or cutover window. This is one of the Microsoft 365 mailbox migration methods larger organizations use when mailboxes need to remain accessible in both environments over a longer migration timeline, and it requires directory synchronization and the Hybrid Configuration Wizard.
IMAP migration
For sources such as Gmail, Zoho, or Zimbra, IMAP migration transfers email content. IMAP is an email-only protocol: calendars and contacts do not transfer through this method and require a separate export and import step, typically CSV for contacts and ICS for calendars.
PST file import
PST files, such as old archives, former-employee mail, or exports from a decommissioned server, can be imported directly into Office 365 mailboxes, with folder hierarchy and item properties (flags, categories, read/unread state) preserved.
EdbMails as a Migration Partner
Across these methods, tooling determines how the migration actually runs in practice. EdbMails is built to handle the scenarios common in real migrations, including mixed Exchange versions, remote-office connections on slower links, and mailboxes with no clean source inventory.
Supports diverse source environments
Exchange Server , hosted Exchange (Rackspace, GoDaddy, Intermedia, and others), IMAP-capable servers (Gmail, Zimbra, Zoho, IceWarp, cPanel, and others speaking the protocol), and PST files of any size.
User-friendly software interface
The UI doesn't try to be clever. No PowerShell scripting required. Most admins can run their first migration without PowerShell and without sitting through training first. The wizard-driven workflow walks you through source connection, target connection, mapping, and execution in a linear flow that's hard to get wrong.
Core capabilities
Incremental migration that captures deltas without producing duplicates; automatic mailbox mapping tthat pairs source to target by display name, first/last name, and email; granular filters for date range, sender, recipient, attachment name, and read/unread status; and parallel migration runs of up to 20 mailboxes at a time.
Steps to Migrate a Mailbox by Source
The Office 365 mailbox migration steps below are organized by source environment, covering tenant-to-tenant, on-premises Exchange, hosted Exchange, IMAP, and PST scenarios.
Migrate a mailbox to Office 365 from Exchange Online
Tenant-to-tenant migration moves mailboxes, calendars, contacts, tasks, public folders, shared mailboxes, permissions, SharePoint, and OneDrive content from one Office 365 organization to another. Common drivers are mergers and acquisitions, or tenant restructuring.
Steps to migrate a mailbox between Office 365 tenants
Steps 1: Download and install EdbMails
- Run the installer, complete setup, then launch the app and log in or start a free trial.
- Run the installer, complete setup, then launch the app and log in or start a free trial.
Steps 2: Choose Office 365 migration
- Select ‘Office 365 Migration’, then ‘Office 365 to Office 365 Migration’. The job name can be left as default or renamed.
- Select ‘Office 365 Migration’, then ‘Office 365 to Office 365 Migration’. The job name can be left as default or renamed.
Steps 3: Connect the source Office 365 tenant
- Add a new connection or reuse an existing one, authenticate via OAuth 2.0 through Microsoft's sign-in page, then load and select the mailboxes to migrate.
- Add a new connection or reuse an existing one, authenticate via OAuth 2.0 through Microsoft's sign-in page, then load and select the mailboxes to migrate.
Steps 4: Connect target Office 365
- Add or reuse a connection, authenticate, and load the target mailboxes.
- Add or reuse a connection, authenticate, and load the target mailboxes.
Step 5: Map source and target mailboxes
- Auto-mapping matches by display name, first/last name, and email address; override manually for edge cases such as name changes or mailbox consolidation.
- Auto-mapping matches by display name, first/last name, and email address; override manually for edge cases such as name changes or mailbox consolidation.
Step 6: Start the migration
- Monitor progress, pause and resume as needed, and review logs to verify item counts on completion.
- Monitor progress, pause and resume as needed, and review logs to verify item counts on completion.
See the Office 365 to Office 365 migration guide for the full walkthrough, including planning, prerequisites, and post-migration cutover.
Migrate a mailbox to Office 365 from Exchange Server
Exchange to Office 365 migration transfers emails, contacts, calendars, and tasks from an on-premises Exchange environment. Supported source versions are Exchange 2007, 2010, 2013, 2016, 2019, and Small Business Server 2011. No hybrid deployment is required for a direct on-premises-to-cloud path.
Steps to migrate a mailbox from on-premises Exchange Server
Step 1: Install and launch EdbMails
- Select ‘Live Exchange Migration’, then ‘Live Exchange to Office 365 Migration’.
- Select ‘Live Exchange Migration’, then ‘Live Exchange to Office 365 Migration’.
Step 2: Connect the source Exchange server
- Add or reuse a connection, sign in, then auto-detect or CSV-load and select the mailboxes to migrate.
- Add or reuse a connection, sign in, then auto-detect or CSV-load and select the mailboxes to migrate.
Step 3: Connect target Office 365
- Authenticate through Microsoft's sign-in page and load the target mailboxes.
- Authenticate through Microsoft's sign-in page and load the target mailboxes.
Step 4: Map Exchange to Office 365 mailboxes
- Target mailboxes and license assignments are created automatically; mapping is automatic with manual override available.
- Target mailboxes and license assignments are created automatically; mapping is automatic with manual override available.
Step 5: Start the migration
- Monitor live progress, review the migration report on completion, and verify the content landed as expected on the target.
- Monitor live progress, review the migration report on completion, and verify the content landed as expected on the target.
Migrate a mailbox to Office 365 from Hosted Exchange Server
Organizations on hosted Exchange (Rackspace, GoDaddy, Intermedia, and similar providers) typically move to Office 365 for administrative control the hosted model does not provide. Hosted Exchange to Office 365 migration transfers emails, contacts, calendars, and tasks intact.
Steps to move hosted Exchange to Office 365
Step 1: Install and launch EdbMails
- Select Live Exchange Migration, then ‘Live Exchange to Office 365 Migration’
- Select Live Exchange Migration, then ‘Live Exchange to Office 365 Migration’
Step 2: Connect the source hosted Exchange server
- Choose Connect to Hosted Exchange server, then connect via Autodiscover email or a manual connection using the server's FQDN or IP. For multiple mailboxes, use the Full Access permission option to avoid signing in per mailbox. Load and select mailboxes.
- Enter the source hosted Exchange credentials and log in.
- Load the mailboxes, either automatically or by importing a CSV file. Select the ones you want to migrate, then click Next.
- Choose Connect to Hosted Exchange server, then connect via Autodiscover email or a manual connection using the server's FQDN or IP. For multiple mailboxes, use the Full Access permission option to avoid signing in per mailbox. Load and select mailboxes.
Step 3: Connect target Office 365
- Authenticate via OAuth and load target mailboxes.
- Authenticate via OAuth and load target mailboxes.
Step 4: Map hosted Exchange to Office 365 mailboxes
- Auto-mapping pairs source and target; manual control is available for specific mailboxes or folders.
- Auto-mapping pairs source and target; manual control is available for specific mailboxes or folders.
Step 5: Start the migration
- Monitor live progress, review the migration report, and verify mailboxes and folders on the target.
- Monitor live progress, review the migration report, and verify mailboxes and folders on the target.
Migrate a mailbox to Office 365 from an IMAP server
Any source that speaks IMAP, including Gmail, IceWarp, Zoho, Zimbra, and cPanel, can migrate to Office 365 through the IMAP protocol. The native IMAP migration in the Microsoft 365 admin center is suitable for smaller projects; for larger volumes, or where batch retries, granular filtering, or auto-reconnect on network drops are needed, the EdbMails workflow provides more control.
IMAP migration moves email only. Calendars and contacts require a separate export and import step, which should be planned alongside the IMAP migration rather than after it.
Steps to migrate a mailbox from an IMAP-enabled server
Step 1: Download and install EdbMails
- Select ‘Google Workspace and IMAP Migrations’, then ‘IMAP to Office 365 Migration’.
- Select ‘Google Workspace and IMAP Migrations’, then ‘IMAP to Office 365 Migration’.
Step 2: Connect the source IMAP server
- For a single mailbox, connect via IMAP or POP3 directly (Gmail requires an app password when 2FA is enabled). For bulk migration, use the CSV template listing email, password, host, and port per account.
- For a single mailbox, connect via IMAP or POP3 directly (Gmail requires an app password when 2FA is enabled). For bulk migration, use the CSV template listing email, password, host, and port per account.
Step 3: Select source IMAP mailboxes
- Choose mailboxes or folders to migrate.
- Choose mailboxes or folders to migrate.
Step 4: Connect target Office 365
- Authenticate via OAuth 2.0 and load target mailboxes.
- Authenticate via OAuth 2.0 and load target mailboxes.
Step 5: Map source and target mailboxes
- EdbMails handles mailbox and folder mapping and creates target mailboxes in Office 365 if they do not exist.
- EdbMails handles mailbox and folder mapping and creates target mailboxes in Office 365 if they do not exist.
Step 6: Start the migration
- Monitor progress and review the log for mailbox-by-mailbox status and per-folder item counts on completion.
- Monitor progress and review the log for mailbox-by-mailbox status and per-folder item counts on completion.
Migrate a mailbox to Office 365 from an Outlook PST file
PST to Office 365 import writes Outlook PST content directly into Office 365 mailboxes, including emails, contacts, calendars, and tasks, with folder hierarchy preserved.
Steps to move PST files into Office 365 mailboxes
Step 1: Install EdbMails
- Review system requirements before processing large PST files.
- Review system requirements before processing large PST files.
Step 2: Launch and choose the migration type
- Select Office 365 Migration, then Restore PST to Office 365.
- Select Office 365 Migration, then Restore PST to Office 365.
Step 3: Add PST files
- Browse to and select PST files, verify the list, and optionally enable target-folder-per-PST naming for mailboxes receiving multiple archives.
- Browse to and select PST files, verify the list, and optionally enable target-folder-per-PST naming for mailboxes receiving multiple archives.
Step 4: Connect target Office 365
- Authenticate and load target mailboxes.
- Authenticate and load target mailboxes.
Step 5: Map PSTs to Office 365 mailboxes
- Auto-mapping pairs PST files with target mailboxes by name; manual override is available.
- Auto-mapping pairs PST files with target mailboxes by name; manual override is available.
Step 6: Start the PST import
- Review the log for the full report on completion.
- Review the log for the full report on completion.
Why EdbMails for Moving Mailboxes to Office 365
- Incremental migration
The first run is a full migration; every subsequent run migrates only new or changed items, so no duplicates land on the target. This matters because most real migrations happen over multiple passes: an early seed migration followed by a final delta run on cutover day.
- Safe and secure migration
Migration runs server-to-server with no intermediate storage and no third-party servers in the path. Credentials are not stored; sign-in goes through Microsoft's own flow. EdbMails holds ISO/IEC 27001 certification and GDPR-compliant data handling practices.* Authentication uses OAuth 2.0 modern auth with TLS encryption in transit.
- Scalable, high-performance migration
From a single folder to a full tenant of thousands of mailboxes, multithreading handles parallel jobs and automatic throttling management works within the rate limits Microsoft imposes. Up to 20 mailboxes can run in parallel, with a mailbox-by-mailbox log to verify completion.
- Multilingual support
Mailbox content in any language and script migrates without altering folder names, structure, or special characters on the target.
- Zero downtime
Your users keep working throughout the migration, without ever losing access to their email. Everything copies over quietly, and once it's done, you simply switch everyone to the new tenant. There's no outage and no interruption. This matters most when key people, like your CFO, are among those being moved. See our zero-downtime model page.
Frequently Asked Questions (FAQ)
What are the prerequisites for migrating mailboxes to Office 365 with EdbMails?
EdbMails installed on a Windows machine, admin access to source and target environments, valid credentials on both sides (a global admin account or a user with Full Access Office 365), stable network connectivity, and a machine meeting the system requirements for the EdbMails version in use.
Can I migrate from an on-premises Exchange server to Office 365?
Yes, directly, from Exchange 2007, 2010, 2013, 2016, 2019, or Small Business Server 2011 to Office 365, with no hybrid setup required.
Can I perform a staged migration with EdbMails?
Yes, staged migration is supported, moving mailboxes in batches instead of all at once, which suits larger rollouts where a single cutover window is not preferred.
Can I migrate from other email servers like Gmail or Zimbra to Office 365?
Yes, any source that speaks IMAP works, including Gmail, Zimbra, Yahoo, and others, with Office 365 as the target.
What support is available during the migration process?
Support is available through live chat, email, and phone, with remote sessions available if needed.
How can I verify the migration was successful?
Check the log report for item counts per folder and per mailbox, comparing source and target. Spot-check a few larger mailboxes in Outlook or OWA to confirm the folders and counts match expectations.
Does EdbMails migrate calendar items and contacts?
Yes. All of it. Emails, calendars, contacts, tasks, notes, journals. Nothing gets left behind on the source side. The one exception is IMAP source migrations — IMAP only carries email, so calendars and contacts from IMAP sources need a separate export-import path.
Can I pause and resume the migration process?
Yes. Pause and resume works at any point works at any point without losing progress.
What happens if there is intermittent internet during migration?
The migration pauses automatically when the connection drops and resumes when it returns, without producing duplicates or losing progress.
Are there any post-migration steps I need to follow?
Point user accounts and Outlook profiles at the new Office 365 environment and confirm folders read as up to date. Assign licenses to every migrated mailbox promptly, since Microsoft disables unlicensed mailboxes after 30 days. Configure Autodiscover DNS records in the target tenant so Outlook and mobile clients connect correctly. Only after the migration is verified complete, every mailbox is licensed, and users are working from the new tenant, decommissioning the source environment.
Does EdbMails migrate Inbox Rules during migration?
Yes. Inbox Rules carry across with the mailbox, so users keep their existing rules on the target without setting them up again. Rules that point to accounts outside the migration scope need to be reconfigured manually on the target.
For migrating a large number of mailboxes at once, see bulk Office 365 mailbox migration. For full mailbox migration tool capabilities, including mapping, parallel processing, and reporting, see Office 365 Migration Software.
