MailtoPst
FR
OLM IMAP

Convert OLM to IMAP
Online Tool

Migrate Outlook for Mac OLM files to any IMAP server. Convert OLM to EML or MBOX with MailtoPst, then upload to your IMAP mailbox. No Windows needed.

Convert now → See how it works
🛡️ GDPR Compliant 🔒 TLS 1.3 Encryption 🇪🇺 Hosted in EU 🇫🇷 Built in France 🗑️ Auto-delete 24h

What is a OLM file?

OLM (Outlook for Mac) is the export/archive format exclusive to Microsoft Outlook on macOS. When you export data from Outlook for Mac, it creates an .olm file — a ZIP-based container that stores emails, contacts, calendar events, tasks, and notes.

OLM files are relevant for IMAP migration when:
- Switching from Outlook Mac to another platform — moving away from Microsoft's ecosystem entirely
- Migrating to a self-hosted mail server — setting up Dovecot, Postfix, or Zimbra and importing historical email from Outlook Mac
- Consolidating email on a central server — uploading local Outlook Mac archives to an IMAP-accessible server
- Preserving email from a departing employee — extracting email data from a Mac before returning the hardware

OLM files cannot be opened by Windows Outlook, Thunderbird, or any non-Mac application. Conversion to a universal format is mandatory for IMAP import.

What is a IMAP file?

IMAP (Internet Message Access Protocol) is the standard protocol that allows email clients to access messages stored on a remote mail server. IMAP keeps all emails on the server and synchronizes them to connected clients in real-time.

Uploading OLM emails to an IMAP server delivers:
- Cross-platform access — emails accessible from macOS, Windows, Linux, iOS, and Android
- Multiple client support — Thunderbird, Apple Mail, Outlook, and any IMAP-compatible app
- Server-side safety — emails backed up on the server rather than locked in a local file
- Real-time synchronization — changes made on one device appear on all others
- Provider choice — works with Gmail, Fastmail, Zimbra, Dovecot, and any IMAP service

After importing your OLM emails to an IMAP server, you are free to use any email client on any device — no longer restricted to Outlook for Mac.

Why convert OLM to IMAP?

Migrating OLM data to an IMAP server resolves common pain points for Mac Outlook users:

1. Breaking free from platform lock-in
OLM files are exclusive to Outlook for Mac. By importing to an IMAP server, your emails become accessible from any email client on any operating system.

2. Team collaboration across platforms
In mixed Mac/Windows environments, OLM files from Mac users cannot be shared with Windows colleagues. Moving emails to a shared IMAP server eliminates this cross-platform barrier.

3. Transitioning to open-source email clients
Users switching from Outlook Mac to Thunderbird, Apple Mail, or other clients need their email history available via IMAP. The OLM file must be converted and uploaded to make this possible.

4. Corporate compliance and centralization
IT departments need visibility into all email data. OLM files stored locally on Mac laptops are invisible to compliance tools. Uploading to a managed IMAP server brings this data under centralized governance.

5. Data preservation during hardware changes
When upgrading or replacing Mac hardware, exporting to OLM and uploading to an IMAP server ensures email data survives the transition independently of any specific machine.

OLM vs IMAP — Key Differences

Feature OLM IMAP
Platform macOS only (Outlook for Mac) Any OS, any device
Format ZIP-based archive (proprietary) Open protocol (RFC 3501)
Client support Outlook for Mac exclusively Every IMAP email client
Data location Local Mac hard drive Remote server (cloud or on-prem)
Sharing Cannot share with Windows users Accessible to all users
Backup Manual file backup Server-managed backup

3 methods to convert OLM to IMAP

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

Upload the OLM file to MailtoPst and convert to MBOX format. Install Thunderbird, configure your IMAP account, then import the MBOX file and drag the emails into your IMAP folders.

Pros

  • ✓ Works on Mac natively
  • ✓ No Windows or Outlook needed
  • ✓ Thunderbird is free
  • ✓ Works with any IMAP server

Cons

  • ✗ Requires Thunderbird installation
  • ✗ IMAP upload can be slow for large volumes
  • ✗ Two-step process

Method 2: Convert OLM to EML, upload via IMAP client

Use MailtoPst to convert the OLM to individual EML files. Then use any IMAP email client (Thunderbird, Apple Mail, etc.) to import the EML files into your IMAP server by dragging them into the appropriate folders.

Pros

  • ✓ Fine-grained control over import
  • ✓ Preview emails before uploading
  • ✓ Works from any browser for conversion
  • ✓ GDPR compliant, EU servers

Cons

  • ✗ Slower for large archives
  • ✗ Manual folder organization
  • ✗ Requires email client setup
Recommended

Method 3: Server-side MBOX import (admin)

Convert OLM to MBOX with MailtoPst, then transfer the MBOX files to the IMAP server. Use doveadm (Dovecot), zmmailbox (Zimbra), or other server-side tools to import the MBOX directly into user mailboxes.

Pros

  • ✓ Fastest for large archives
  • ✓ No client-side bottleneck
  • ✓ Batch import multiple mailboxes
  • ✓ Preserves all metadata

Cons

  • ✗ Requires server SSH/admin access
  • ✗ Technical expertise needed
  • ✗ Server-specific tools vary
Try MailtoPst →

Step by step

How to convert OLM to IMAP with MailtoPst

01

Upload your OLM file

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

02

Choose IMAP as output

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

03

Download your IMAP file

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

Convert your OLM to IMAP now →

100 MB free credit. No credit card required.

FAQ

Frequently Asked Questions

Can I import an OLM file directly to an IMAP server?

No. OLM is a proprietary Outlook for Mac format that no IMAP server can read. You must first convert the OLM to MBOX or EML using MailtoPst, then import the converted files to your IMAP server.

Do I need Windows to convert OLM files?

No. MailtoPst is a web-based tool that works from any browser on any operating system. Upload your OLM file from your Mac, convert it to MBOX or EML, and download the result — all without leaving macOS.

Will the OLM folder structure be preserved on my IMAP server?

Yes. MailtoPst maintains the original folder hierarchy from the OLM file. When imported via an IMAP client, these folders are recreated on your IMAP server as IMAP mailbox folders.

What about contacts and calendar from the OLM?

MailtoPst focuses on email migration. Calendar data can be exported from Outlook for Mac as ICS files and imported into your calendar app. Contacts can be exported as VCF files. These are separate from the IMAP email import.

How large of an OLM file can I convert?

MailtoPst supports OLM files up to 50 GB with resumable upload technology. The conversion runs on powerful EU-based servers, so even large archives are processed quickly. Files are auto-deleted within 24 hours for GDPR compliance.

Related conversions

EML → MBOX OLM → MBOX OLM → PST OST → IMAP PST → IMAP
See all 30 conversion paths →

Ready to convert your emails?

First conversion free. No credit card required.

Start converting → See pricing