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Need help? Reach us at
+1 (855) 418-2323
File Converters TIFF and PDF apps Forensic FreewareThe free online mail converter that transforms EML, MSG, PST, and MBOX files into PDF, HTML, Word, and more — no software required.
CoolUtils online mail converter supports all major email formats as input — EML, MSG, PST, OST, and MBOX — and converts them to PDF, HTML, DOC, TXT, JPEG, and other output formats. Upload the file, select the output format, and download the converted document in seconds. No installation, no registration, completely free.
1) Upload OST file to convert
Drop files here, or Click to select
Allowed file types: pst, ost, eml, msg, mime, smime, p7m, mbox, dbx, vcf, vmbx, opf, asice, cpgz, lzh, zcf
2) Set converting OST to PDF options
3) Get converted file
Total Outlook Converter
Convert Outlook emails from multiple sources to a variety of formats.Filter emails by sender, subject, date, keywords, and more.Useful data saving options - convert only necessary data from your emails.Unique output files formatting options specify how your files will look.Affordable Price - pay once for a lifetime license with no hidden fees.Command Line Support - convert emails via command line.Fast batch conversion - convert multiple emails simultaneously.High security options - protect your output PDF files (if you choose PDF).Various file naming and date saving options - organize your output files easily.Variety of attachment saving options - choose how to save attachments.Trust - you can rely on powerful email converters from CoolUtils.Easy to use even for beginners - enjoy clear user-friendly interface.💾 Upload Your File: Go to the site, click on «Upload File,» and select your OST file.
✍️ Set Conversion Options: Choose PDF as the output format and adjust any additional options if needed.
Convert and Download: Click 👉«Download Converted File»👈 to get your PDF file.
| File extension | .OST |
| Category | File |
| Description | OST is an offline data file used by Microsoft Outlook to store emails, calendars, and other information when working in cached mode with an Exchange server. |
| Associated programs | Microsoft Outlook, SysTools OST Viewer, Kernel OST Viewer |
| Developed by | Microsoft |
| MIME type | application/vnd.ms-outlook |
| Useful links | More detailed information on OST files |
| Conversion type | OST to PDF |
| File extension | |
| Category | Document File |
| Description | Adobe Systems Portable Document Format (PDF) format provides all the contents of a printed document in electronic form, including text and images, as well as technical details like links, scales, graphs, and interactive content. You can open this file in free Acrobat Reader and scroll through the page or the entire document, which is generally one or more pages. The PDF format is used to save pre-designed periodicals, brochures, and flyers. |
| Associated programs | Adobe Viewer Ghostscript Ghostview Xpdf CoolUtils PDF Viewer |
| Developed by | Adobe Systems |
| MIME type | application/pdf application/x-pdf |
| Useful links | More detailed information on PDF files |
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OST is the offline cache Outlook builds for an Exchange or Microsoft 365 account. Without the original profile, almost nothing reads it. PDF is the universal page-faithful document format every operating system, browser, and reader opens. Converting OST to PDF rescues cached mail into a format every reviewer, auditor, or archive system can read for the long term. Drop your .ost file above.
OST (Offline Storage Table) is the local cache Outlook maintains for an Exchange, Microsoft 365, IMAP, or Outlook.com account. The file lives under your user profile and mirrors the server-side mailbox so Outlook works offline. OST is encrypted against the original profile — without that profile and that machine, Outlook cannot open it.
PDF (Portable Document Format) is Adobe's universal page-faithful document format, standardised as ISO 32000. Every operating system, every browser, every smartphone, and every printer driver renders PDF natively. PDF preserves typography, images, and pagination exactly as authored, and is the de facto standard for legal and regulatory archives.
| Property | OST | |
|---|---|---|
| Purpose | Offline cache of a server mailbox | Page-described document |
| Tied to profile | Yes (encrypted to the profile) | No |
| Native readers | Outlook with the original account | Every platform and browser |
| Editable | Inside Outlook only | Read-only by default |
| Use after the account is gone | Effectively locked | Fully readable forever |
| Long-term archive | Risky | ISO 32000 standard |
| Typical use | Local cache | Reports, exhibits, archives |
Batch-convert an entire folder without opening the interface:
TotalOutlookConverter.exe C:\ost_files C:\pdf_out /ConvertTo pdf /ProcessRecursively
Add /ProcessRecursively to include subfolders. Save the command in a .bat file for scheduled or automated runs.
| Feature | Online (this page) | Total Outlook Converter (desktop) |
|---|---|---|
| File size limit | 50 MB | Unlimited |
| Batch conversion | One file at a time | Entire folders at once |
| Software install | None required | Windows 7–11 |
| Output options | Standard | Full control |
| Command-line | No | Yes |
| Privacy | File uploaded to server | Stays on your computer |
| Price | Free | From $49.90 |
