MailtoPst
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Email Office 365

Convert Email to Office 365
Online Tool

Migrate emails from any format to Office 365 (Microsoft 365). Convert EML, MBOX, OLM, or MSG files to PST for import. Complete step-by-step migration guide.

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What is a Email file?

When migrating to Office 365, organizations and individuals may have email data stored in various formats from their previous email system:

- EML files — exported from Thunderbird, Windows Mail, or saved individually from webmail
- MBOX archives — from Thunderbird, Gmail Takeout, or Unix mail servers
- OLM files — exported from Outlook for Mac
- MSG files — individual Outlook messages saved outside of a PST
- EMLX files — from Apple Mail on macOS
- PST/OST files — from previous Outlook installations

The path to Office 365 requires converting these various formats into PST (the format Microsoft's Import Service accepts) or into EML/MBOX for IMAP-based import. MailtoPst simplifies this by handling all source formats in one tool.

What is a Office 365 file?

Office 365 (Microsoft 365) is Microsoft's cloud-based productivity platform built around Exchange Online for email. It provides enterprise-grade email hosting with 50-100 GB mailboxes, advanced security, and compliance tools.

After migrating your email data to Office 365:
- Access from anywhere — Outlook Web App, Outlook desktop, and mobile apps
- Centralized administration — IT admins manage mailboxes from one console
- Advanced security — anti-phishing, anti-malware, and data loss prevention
- Compliance features — eDiscovery, litigation hold, and retention policies
- Collaboration tools — Teams, SharePoint, and OneDrive integrate with your mailbox
- Scalability — add or remove users as your organization grows

Office 365 is the destination of choice for organizations standardizing on Microsoft's ecosystem.

Why convert Email to Office 365?

Migrating email from any format to Office 365 is driven by organizational and personal needs:

1. Platform consolidation
Organizations with email data scattered across Thunderbird, Apple Mail, Gmail, and other platforms consolidate everything into Office 365 for unified management.

2. Moving from Google Workspace to Microsoft 365
Companies switching from Google Workspace export their Gmail data as MBOX (via Google Takeout), then convert to PST for Office 365 import.

3. Legacy email system migration
Decommissioning old email servers (Zimbra, Postfix, Dovecot) requires extracting email data and importing it into Office 365 to preserve historical communications.

4. Mac to Windows transition
Organizations standardizing on Windows Outlook need to migrate OLM files from Mac users and EMLX files from Apple Mail users into Office 365 mailboxes.

5. Freelancer and consultant onboarding
New team members joining from diverse email backgrounds bring EML, MBOX, or other format archives that need to be imported into their new Office 365 mailbox.

Email vs Office 365 — Key Differences

Feature Email Office 365
Hosting Varies (local, self-hosted, cloud) Microsoft cloud (Exchange Online)
Management Depends on source system Microsoft 365 admin center
Security Varies widely Enterprise-grade (ATP, DLP)
Compliance Varies eDiscovery, retention, legal holds
Access Depends on format/platform Web, desktop, mobile (anywhere)
Integration Limited Teams, SharePoint, OneDrive

3 methods to convert Email to Office 365

Method 1: Convert to PST with MailtoPst, import via Microsoft Import Service

Upload your email files (EML, MBOX, OLM, MSG, EMLX) to MailtoPst and convert to PST format. Then use the Microsoft 365 Import Service (Network Upload) in the Purview compliance portal to import the PST into Office 365 mailboxes.

Pros

  • ✓ Handles any source format
  • ✓ Official Microsoft import path
  • ✓ Good for bulk migration
  • ✓ No Outlook needed for conversion

Cons

  • ✗ Requires Microsoft 365 admin access
  • ✗ AzCopy tool needed for upload
  • ✗ CSV mapping file required
  • ✗ Multi-step process

Method 2: Convert to PST with MailtoPst, import via Outlook desktop

Convert your email files to PST using MailtoPst. Open the PST in Outlook desktop connected to your Office 365 account, then copy or move emails from the PST into your cloud mailbox.

Pros

  • ✓ No admin access needed
  • ✓ Simple drag-and-drop interface
  • ✓ Works for any end user
  • ✓ Familiar Outlook workflow

Cons

  • ✗ Requires Outlook desktop (Windows)
  • ✗ Slow for large PST files
  • ✗ Manual process for multiple PSTs
Recommended

Method 3: Convert to EML with MailtoPst, upload via IMAP

Convert your email files to EML format with MailtoPst. Connect an IMAP client (Thunderbird, Outlook) to your Office 365 account, then import the EML files into your cloud mailbox through the client.

Pros

  • ✓ No admin access needed
  • ✓ Works from Mac, Linux, Windows
  • ✓ Selective import possible
  • ✓ Free IMAP clients available

Cons

  • ✗ Slower than PST import
  • ✗ IMAP sync overhead
  • ✗ Requires client configuration
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Step by step

How to convert Email to Office 365 with MailtoPst

01

Upload your Email file

Drag & drop or click to upload your .email file. Files up to 51 GB supported with resumable upload.

02

Choose Office 365 as output

Select Office 365 from the format dropdown. MailtoPst auto-detects the best conversion settings.

03

Download your Office 365 file

Conversion takes seconds. Download your .office365 file or receive it by email.

Convert your Email to Office 365 now →

100 MB free credit. No credit card required.

FAQ

Frequently Asked Questions

What is the best format to import into Office 365?

PST is the recommended format for Office 365 import. Microsoft's Import Service is designed specifically for PST files. Convert your EML, MBOX, OLM, or other email files to PST using MailtoPst before importing.

Can I migrate from Gmail to Office 365?

Yes. Export your Gmail data as MBOX using Google Takeout, then convert the MBOX to PST with MailtoPst. Import the PST into Office 365 using the Import Service or Outlook desktop.

Can I migrate from Thunderbird to Office 365?

Yes. Thunderbird stores emails in MBOX format. Locate your Thunderbird profile folder, find the MBOX files, then upload them to MailtoPst to convert to PST. Import the PST into Office 365.

Do I need admin access for the migration?

For the Microsoft Import Service, yes — you need Global Admin or Mailbox Import Export role. For end-user import via Outlook desktop, no admin access is needed — just open the PST and drag emails into your cloud mailbox.

How large of an email archive can I migrate to Office 365?

MailtoPst supports source files up to 50 GB. Office 365 mailboxes range from 50 GB to 100 GB depending on your plan, with optional auto-expanding archive mailboxes for even more storage.

Related conversions

Email → PST EML → PST MBOX → PST OST → Office 365 PST → Office 365
See all 30 conversion paths →

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