MailtoPst
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PST IMAP

Convert PST to IMAP
Online Tool

Upload Outlook PST emails to any IMAP server. Convert PST to EML or MBOX with MailtoPst, then sync to your IMAP mailbox. Works with any provider.

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What is a PST file?

PST (Personal Storage Table) is a proprietary Microsoft Outlook format that stores email messages, calendar entries, contacts, and tasks in a single local file. PST files are the standard export format for Microsoft Outlook on Windows and are commonly used for email backup and archival.

PST files need to be imported to IMAP servers when:
- Switching email providers — moving from Outlook to a new IMAP-based email service
- Setting up a self-hosted mail server — deploying Postfix, Dovecot, or Zimbra and needing to import historical email
- Centralizing email archives — uploading local PST backups to a cloud-accessible IMAP server
- Migrating to hosted email — moving to providers like Fastmail, ProtonMail, or corporate IMAP servers

Since IMAP servers do not accept PST files directly, conversion to a compatible format (EML or MBOX) is the essential first step.

What is a IMAP file?

IMAP (Internet Message Access Protocol) is the standard protocol used by virtually all modern email servers and clients to access and manage email. Unlike POP3 which downloads emails to a single device, IMAP keeps emails on the server and synchronizes them across all connected devices.

IMAP is used by nearly every email provider:
- Gmail, Outlook.com, Yahoo Mail — all major free email services
- Fastmail, ProtonMail, Tutanota — privacy-focused providers
- Corporate servers — Exchange, Zimbra, Postfix/Dovecot setups
- Self-hosted solutions — personal mail servers running on VPS or dedicated hardware

By uploading your PST emails to an IMAP server, they become accessible from any email client on any device — Thunderbird, Apple Mail, mobile apps, and webmail interfaces all connect via IMAP.

Why convert PST to IMAP?

Importing PST data to an IMAP server unlocks several important benefits:

1. Universal accessibility
PST files are only accessible through Microsoft Outlook on Windows. By uploading the emails to an IMAP server, they become available on every email client and device — phones, tablets, Macs, Linux machines, and any web browser.

2. Provider independence
IMAP is an open standard supported by every email client. Whether you switch to Thunderbird, Apple Mail, Fastmail, or any other service, your emails remain accessible without further conversion.

3. Self-hosted email migration
System administrators deploying Postfix, Dovecot, or other open-source mail servers need to import historical email data. Converting PST to EML and uploading via IMAP is the most reliable method.

4. Multi-device synchronization
Unlike a local PST file, emails stored on an IMAP server synchronize automatically across all connected devices. Read status, folders, and flags are kept in sync everywhere.

5. Backup diversification
Uploading PST archives to an IMAP server creates a live, searchable backup that complements local file storage.

PST vs IMAP — Key Differences

Feature PST IMAP
Protocol Proprietary file format Open standard (RFC 3501)
Access Single device (Outlook only) Any device, any client
Sync No sync (local file) Real-time multi-device sync
Storage Local disk Server-side (cloud or on-premises)
Client support Microsoft Outlook only Every modern email client
Vendor lock-in Microsoft ecosystem Provider-independent

3 methods to convert PST to IMAP

Method 1: Convert PST to EML with MailtoPst, then upload via IMAP client

Convert your PST to individual EML files using MailtoPst. Then use Thunderbird or another IMAP-capable email client connected to your IMAP server and import the EML files by dragging them into the appropriate folders.

Pros

  • ✓ Works with any IMAP server
  • ✓ Selective import possible
  • ✓ No server-side tools needed
  • ✓ Cross-platform (Mac, Windows, Linux)

Cons

  • ✗ Slow for very large archives
  • ✗ Requires IMAP client installation
  • ✗ Manual folder organization needed

Method 2: Convert PST to MBOX with MailtoPst, use server-side import

Convert the PST to MBOX with MailtoPst. If you have server access, use tools like mb2md, doveadm, or the Zimbra admin console to import the MBOX files directly into the IMAP server's mailbox storage.

Pros

  • ✓ Fastest method for large archives
  • ✓ No IMAP sync bottleneck
  • ✓ Preserves folder structure
  • ✓ Batch processing possible

Cons

  • ✗ Requires server-side access (SSH/admin)
  • ✗ Technical knowledge needed
  • ✗ Server-specific commands vary
Recommended

Method 3: Use imapsync with converted output

Convert PST to EML or MBOX with MailtoPst. Set up a temporary local IMAP server (e.g., Dovecot) with the converted files, then use imapsync to mirror the data to your production IMAP server. Ideal for large-scale server-to-server migration.

Pros

  • ✓ Best for large-scale migrations
  • ✓ Reliable and resumable
  • ✓ Preserves all metadata
  • ✓ Industry-standard tool

Cons

  • ✗ Advanced technical setup required
  • ✗ imapsync requires Perl
  • ✗ Temporary server needed
  • ✗ Not suitable for non-technical users
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Step by step

How to convert PST to IMAP with MailtoPst

01

Upload your PST file

Drag & drop or click to upload your .pst 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 PST to IMAP now →

100 MB free credit. No credit card required.

FAQ

Frequently Asked Questions

Can I import a PST file directly to an IMAP server?

No. IMAP servers do not understand the PST format. You need to convert the PST to EML or MBOX first using MailtoPst, then import the converted files to your IMAP server through a client or server-side tool.

Which IMAP servers are compatible with this migration?

Any IMAP server works: Dovecot, Cyrus, Courier, Zimbra, Exchange Online, Gmail, Fastmail, ProtonMail Bridge, and more. The conversion output (EML/MBOX) is a universal format understood by all email systems.

Will my folder hierarchy be preserved on the IMAP server?

Yes. MailtoPst preserves the original PST folder structure during conversion. When you import via an IMAP client, each folder is recreated on the IMAP server. Most IMAP servers support nested folders matching your original hierarchy.

How do I handle a very large PST file (10+ GB)?

For large PST files, the server-side MBOX import method is fastest. Convert with MailtoPst (supports up to 50 GB), then use doveadm or similar server tools to import. If using a client-side approach, be patient — IMAP uploads process about 1-2 GB per hour.

Do I need Outlook to convert PST for IMAP import?

No. MailtoPst reads PST files entirely server-side. You upload the PST from any browser on any operating system, and download EML or MBOX files ready for IMAP import. No Microsoft software required.

Related conversions

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