Exchange Online PST File Migration — Microsoft 365 Mailbox Import
IT Partner performs Outlook .pst file migration to Microsoft 365 (Exchange Online) for organizations that need to move email, tasks, calendars, and contacts from .pst files into Exchange Online mailboxes.
What this engagement is
This service migrates Outlook .pst file content to Microsoft 365 (Exchange Online). Importing .pst files to user mailboxes can move an organization’s email, tasks, calendars, and contacts into Exchange Online. IT Partner can import .pst files in one of two ways: upload the data files over the network to temporary storage in the Microsoft cloud, or copy the .pst files to a hard drive with BitLocker encryption and physically ship the drive to Microsoft. Export and collection of .pst files can be performed either by IT Partner or the Client, upon agreement.
Success criteria
What you receive
How the work unfolds
Review project scope, stakeholders, PST inventory, mailbox targets, assumptions, risks, and overall project approach.
Validate PST files, confirm mailbox ownership, and approve the PST-to-mailbox mapping plan before import activities begin.
Verify Exchange Online mailbox availability, mailbox capacity, required permissions, licensing, and import prerequisites.
Configure Microsoft 365 Import Service settings, create import jobs, and prepare the import environment for execution.
Import a representative subset of PST files into selected mailboxes to validate import methodology and expected outcomes.
Review pilot import results with stakeholders and obtain approval to proceed with full production imports.
Import all approved PST files into their designated Exchange Online mailboxes according to the approved migration plan.
Verify that imported emails, folder structures, attachments, and historical content are present and accessible within target mailboxes.
Designated users confirm successful access to imported data and validate that historical content is searchable and usable.
Provide import reports, exception logs, validation results, and summary documentation detailing project outcomes.
Review final results, resolve outstanding issues within scope, obtain formal customer acceptance, and close the project.
Prerequisites
Who does what
IT Partner
- Hold a kickoff meeting to exchange contact information, plan key steps, and discuss the project
- Prepare .pst files for downloading in the selected manner
- Provide new Exchange Online mailboxes by creating Microsoft 365 user accounts and assigning Exchange Online user licenses
- Add and validate email domain(s) to Microsoft 365
- Start a migration batch
- Provide a report with the number of mailboxes that were successfully migrated and those that cannot be migrated, if any
- Set up incremental mailbox synchronization to receive any emails sent after the start of the main synchronization
- Resolve any migration issues and errors to ensure that all mailboxes have been successfully migrated
- Change DNS settings and control their application
- Monitor health and status of the destination Exchange Online environment to make sure the migration process is correct
Your team
- Export and collect .pst files (may be performed either by IT Partner or the Client, upon agreement)
- Provide a dedicated point of contact responsible for working with IT Partner and coordinate any outside vendor resources and schedules
- Configure all network equipment, such as load balancers, routers, firewalls, and switches
- Provide the authorization data necessary to complete the migration
- Ensure that contacts and calendars are exported to .pst files (if the export was performed by the Client)
- Perform changes to internal and external DNS, as required
- Assist with identification of high-risk users (top executives and VIP users, users with 50 GB mailboxes or larger and/or 30 GB deleted folders or larger)
- Review and approve engagement deliverables in a timely manner
What's not included
Limitations & technical notes
Frequently asked questions
What types of Outlook data can be migrated from PST files to Exchange Online?
This service migrates Outlook .pst file content such as email, tasks, calendars, and contacts into Microsoft 365 Exchange Online mailboxes. Contacts and calendars must be included in the exported .pst files if the Client performs the export, because IT Partner can only import content that is present in the provided PST files.
How long does the Exchange Online PST migration service take?
The stated duration for IT Partner’s Exchange Online PST file migration service is 1 week. The actual project plan may vary depending on the organization’s needs, PST file readiness, DNS timing, authorization availability, and any migration issues that need resolution.
What business impact or downtime should we expect during the migration?
The service content does not specify a fixed downtime window, so downtime or user impact should be confirmed with IT Partner during planning. The engagement includes Exchange Online health monitoring and migration issue resolution to help ensure the import process is correct.
What reports are provided after the PST migration?
IT Partner provides a report showing the number of mailboxes that were successfully migrated and any mailboxes that cannot be migrated, if applicable. IT Partner also provides a project closeout report with final project status, evidence of matching acceptance criteria, outstanding issues if any, and the final budget.
Does this service include Exchange Online Protection configuration?
No. Exchange Online Protection configuration is not part of PST migration work — importing .pst files does not change how your mail is filtered, and your existing protection settings stay as they are. If you need EOP reviewed or configured, that is scoped as separate work.
What happens if some mailboxes or PST files cannot be migrated successfully?
IT Partner resolves migration issues and errors as part of the service to help ensure all mailboxes are successfully migrated. If any mailboxes cannot be migrated, the reporting deliverable identifies the number of successfully migrated mailboxes and those that cannot be migrated, if any.