We compared the leading tools for opening PST, OST, MSG and EML files without Microsoft Outlook — Outlook Viewer, SysTools, Kernel, Stellar, Aryson and Outlook itself — on formats, search, export, privacy and price. One comes out ahead for anyone who just needs to open a mailbox and read it.
Of every tool we tested, CoolUtils Outlook Viewer offers the best balance for simply opening and reading Outlook data: it opens the widest set of formats (PST, OST, MSG, EML/EMLX, MBOX), is free to browse and search, keeps every message on your own PC, and adds clean export to PDF/HTML/TXT/CSV when you need it in the Pro edition.
It's the best pick for IT admins, forensics/e‑discovery teams and everyday users who need reliable access to a mailbox without buying or installing Microsoft Outlook.
Download Outlook ViewerHow the most popular tools for opening PST/OST/MSG/EML stack up on the features that matter when you just need to read a mailbox.
| Feature | Outlook ViewerCoolUtils | SysToolsPST Viewer | KernelPST Viewer | StellarViewer/Repair | ArysonPST Viewer | MS Outlookbaseline |
|---|---|---|---|---|---|---|
| Opens PST & OST without Outlook | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ |
| Opens MSG / EML / EMLX | ✓ | Separate tool | Separate tool | Partial | Separate tool | MSG only |
| Opens MBOX mailboxes | ✓ | Limited | Limited | ✗ | Limited | ✗ |
| Browse folders & preview attachments | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Instant search (sender / subject / date / phrase) | ✓ | ✓ | Partial | ✓ | Partial | ✓ |
| Free to view / browse | ✓ Free | ✓ | ✓ | ✗ | Partial | ✗ |
| Export to PDF / HTML / TXT | ✓ Pro | Paid | Paid | Paid | Paid | Print only |
| Export to CSV / extract attachments | ✓ Pro | Paid | Paid | Paid | Paid | ✗ |
| 100% offline — files stay on your PC | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Handles large multi-GB PST files | ✓ | ✓ | ✓ | ✓ | Partial | Partial |
| Portable / IT-friendly deployment | ✓ | Partial | Partial | ✗ | Partial | ✗ |
| Windows 11 / 10 / 8 / 7 | ✓ | ✓ | ✓ | ✓ | ✓ | Modern only |
| Price | Free · Pro upgrade | ~$49+ | ~$49+ | ~$79+ | ~$49+ | License / M365 |
✓ Full support · Partial / paid / limited · ✗ Not available
Competitor prices are approximate and vary by edition and licensing — verify on each vendor's site before purchase. Microsoft and Outlook are trademarks of Microsoft Corporation.
How Outlook Viewer compares against each major alternative — and where it pulls ahead.
SysTools offers a well-known free PST viewer with a clean preview and mailbox tree — a solid tool for a quick look at a single store. But its EML/MSG viewing lives in separate products, and any exporting or saving is pushed into a paid edition.
Outlook Viewer opens PST, OST, MSG, EML and MBOX in one app, is free to browse and search, and keeps export in a single affordable Pro upgrade instead of a family of separate tools.
Kernel's free viewer is good at opening damaged or orphaned PST files and previewing items — a strength if recovery is your main concern. However, search is more limited and, again, exporting requires a separate paid Kernel product.
Outlook Viewer combines fast search, broad format support and free browsing, with clean built-in export in Pro rather than a second purchase.
Stellar is best known for its powerful PST repair engine — if your file is badly corrupted, that heavy-duty recovery is genuinely useful. But it is a paid, repair-oriented suite, and simply reading a healthy mailbox is more tool (and more cost) than most people need.
For everyday viewing and light export, Outlook Viewer is free to browse, far lighter, and easier to hand to a non-technical user.
Aryson's viewer previews attachments and handles common Outlook items, and it's a reasonable free option for a one-off look. It is less widely used, though, its search is basic, and export is capped in the trial until you buy.
Outlook Viewer is a more established CoolUtils product (tools trusted since 2003), with stronger search, more formats and predictable free-to-view licensing.
Outlook itself renders your mail perfectly — it's the source application. But it requires a paid license or Microsoft 365 subscription, a full install and a configured mail profile, and it cannot cleanly open an orphaned OST or a stray MBOX at all.
Outlook Viewer opens those files instantly with nothing to configure, no license to buy just to read, and no risk of altering the live mailbox.
Six reasons people pick it over every alternative in this comparison.
PST, OST, MSG, EML/EMLX and MBOX — all opened in a single viewer, instead of juggling a different tool for each file type.
Browse, read and search your mailbox for free. You only pay if you need the Pro export features — not just to open a file.
Everything runs locally — no uploads, no servers. Ideal for confidential mailboxes, e‑discovery and forensic work.
Filter by sender, subject, date range or phrase and get instant results — even inside large, long-threaded mailboxes.
Save messages to PDF, HTML, TXT or CSV and extract attachments — tidy output for reporting, archiving and disclosure.
Runs on standard user accounts with a portable option and easy deployment — no Outlook, no mail profile, no heavy install.
Weighted across format range, search, export, privacy, ease of use and price.
Best overall — the all-round winner
Solid, but export is paid & split
Great for recovery, weaker search
Strong repair, paid & heavy
Basic, lesser-known
Needs license, install & profile
For opening PST, OST, MSG and EML without Microsoft Outlook, CoolUtils Outlook Viewer is our top pick — it opens the widest range of formats, is free to browse and search, keeps data local, and adds clean export in the Pro edition.
No. Outlook Viewer — like SysTools, Kernel, Stellar and Aryson — reads PST/OST directly with no Outlook installed. Unlike Outlook itself, it can also open an orphaned OST with no mail profile.
Many rivals are free to browse but lock exporting and saving behind a paid tool. Outlook Viewer is genuinely free to open, browse and search — only the Pro export features (PDF/HTML/TXT/CSV, attachment extraction) are paid.
Yes. Everything runs locally on your machine with no uploads, so mailboxes never leave your PC — a key requirement for e‑discovery, legal and IT recovery work.
Yes. Beyond PST and OST, Outlook Viewer opens single MSG messages, EML/EMLX files and MBOX mailboxes in the same app — where most rivals need a separate tool for each.
Windows 11, 10, 8 and 7 (x64/x86). No internet connection is needed after download.
See why Outlook Viewer beats the alternatives. Open PST, OST, MSG, EML and MBOX in minutes — no Outlook, no license just to read.
Free to view · Pro adds export to PDF/HTML/TXT/CSV. Microsoft and Outlook are trademarks of Microsoft Corporation.