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OST Gmail

Convert OST to Gmail
Online Tool

Migrate Outlook OST files to Gmail. Convert offline Exchange cache to MBOX or EML, then import into your Google account. Works even with orphaned OST files.

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🛡️ GDPR Compliant 🔒 TLS 1.3 Encryption 🇪🇺 Hosted in EU 🇫🇷 Built in France 🗑️ Auto-delete 24h

What is a OST file?

OST (Offline Storage Table) is Outlook's local cache file created when connected to Microsoft Exchange or Office 365. Unlike PST files, OST files are locked to a specific Outlook profile and cannot be opened by other applications or even another Outlook installation.

OST files become problematic when:
- The Exchange server is decommissioned — the OST becomes orphaned with no server to sync to
- Switching to Gmail/Google Workspace — you need to extract email data before closing the Exchange account
- Outlook profile corruption — the profile is damaged but the OST file is intact
- Employee departures — company laptops contain OST files with business-critical email history

Because Gmail cannot read OST files, a two-step process is needed: first convert the OST to a Gmail-compatible format (MBOX or EML), then import the converted files into your Gmail account.

What is a Gmail file?

Gmail is Google's flagship email service powering both personal accounts and Google Workspace business accounts. With its advanced search, label-based organization, and seamless integration with Google's productivity suite, Gmail is one of the most popular destinations for email migration.

Gmail offers compelling advantages for users migrating from Exchange/Outlook:
- Universal access — browser, mobile apps, and any IMAP-compatible client
- Powerful search — Google's search technology applied to your email
- Labels over folders — one email can have multiple labels for flexible organization
- Integration — seamless connection to Google Drive, Calendar, Meet, and Chat
- Storage — 15 GB free or up to 5 TB with Google Workspace plans

After importing your OST emails into Gmail, they become fully searchable and accessible across all your devices.

Why convert OST to Gmail?

Migrating OST data to Gmail is necessary in several real-world scenarios:

1. Organization-wide migration to Google Workspace
When companies switch from Microsoft Exchange to Google Workspace, employee mailbox data stored in OST files must be migrated. Since OST files cannot be directly imported, conversion to an intermediate format is required.

2. Recovering orphaned mailbox data
If an Exchange server goes offline permanently, OST files on user workstations are the only remaining copy of email data. Converting these to import into Gmail ensures no data is lost during the platform transition.

3. Freelancers and consultants switching platforms
Individuals who used Outlook through a corporate account often need their email history when transitioning to a personal Gmail account. The OST file from their former employer's Outlook contains years of correspondence.

4. Archival and backup diversification
Storing a copy of your email archive in Gmail provides geographic and platform diversification. If your local OST file is corrupted or lost, the Gmail copy remains accessible.

OST vs Gmail — Key Differences

Feature OST Gmail
Format type Local cache file (binary) Cloud-hosted mailbox
Portability Locked to one Outlook profile Accessible from any device
Requires software Microsoft Outlook + Exchange Web browser only
Search capability Outlook local index Google Search engine
Organization Folders Labels (more flexible)
Offline access Full offline access Gmail offline mode (Chrome)

3 methods to convert OST to Gmail

Method 1: Convert OST to MBOX with MailtoPst, import via Thunderbird

Upload your OST file to MailtoPst and convert it to MBOX format. Then install Mozilla Thunderbird, connect it to your Gmail account via IMAP, and import the MBOX file. Drag emails from the local MBOX folders to your Gmail folders in Thunderbird.

Pros

  • ✓ Works with orphaned OST files
  • ✓ No Outlook needed
  • ✓ Works on Mac, Linux, Windows
  • ✓ Free Gmail account compatible

Cons

  • ✗ Requires Thunderbird installation
  • ✗ IMAP sync can be slow
  • ✗ Two-step process

Method 2: Convert OST to PST, then use Google migration tool

Convert the OST to PST format using MailtoPst, then use the Google Workspace Migration for Microsoft Outlook (GWMMO) tool or the admin console migration tool to import the PST into Gmail.

Pros

  • ✓ Google's official tool handles PST
  • ✓ Preserves folder structure as labels
  • ✓ Good for large archives

Cons

  • ✗ Requires Google Workspace (paid) for admin tool
  • ✗ GWMMO is Windows-only
  • ✗ Two conversion steps needed
Recommended

Method 3: Convert OST to EML, import individual emails

Use MailtoPst to convert the OST file to individual EML files. Then use an IMAP email client to import selected EML files into your Gmail account. This method gives maximum control over which emails to migrate.

Pros

  • ✓ Selective migration possible
  • ✓ Preview each email before import
  • ✓ Works from any OS
  • ✓ GDPR compliant, EU servers

Cons

  • ✗ Tedious for large volumes
  • ✗ Requires IMAP client setup
  • ✗ Slower than bulk methods
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Step by step

How to convert OST to Gmail with MailtoPst

01

Upload your OST file

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

02

Choose Gmail as output

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

03

Download your Gmail file

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

Convert your OST to Gmail now →

100 MB free credit. No credit card required.

FAQ

Frequently Asked Questions

Can I import an OST file directly into Gmail?

No. Gmail does not accept OST files directly. You must first convert the OST to MBOX, EML, or PST format using a tool like MailtoPst, then import the converted files into Gmail through an IMAP client or Google's migration tools.

Do I need Outlook installed to migrate OST to Gmail?

No. MailtoPst reads OST files server-side without requiring Outlook. Upload your OST file from any browser on Mac, Linux, or Windows, and download the converted output ready for Gmail import.

Will my OST folder structure appear in Gmail?

Yes. When you import via IMAP, your folder structure is mapped to Gmail labels. Subfolders become nested labels. For example, 'Projects/ClientA' becomes a label 'Projects/ClientA' in Gmail.

What happens to calendar and contacts in the OST?

Email messages are the primary data migrated. Calendar entries and contacts from OST files require separate handling — you can export them as ICS (calendar) and VCF (contacts) files through Outlook, then import into Google Calendar and Google Contacts respectively.

Is the OST to Gmail migration secure?

Yes. MailtoPst uses TLS 1.3 encryption for file transfers, processes files on EU-based servers, and automatically deletes all data within 24 hours. The conversion is fully GDPR compliant.

Related conversions

EML → MBOX OST → EML OST → MBOX OST → PST PST → Gmail
See all 30 conversion paths →

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