MSG file conversions fail for specific, diagnosable reasons. Unlike a vague “something went wrong” error, most MSG conversion failures have a direct cause — and most of those causes have a fix. This guide goes through the most common failure modes, what’s actually happening under the hood in each case, and what to do about it.
The File Size Is Too Large
This is the most common and most straightforward failure cause. MSG files can get large when they contain embedded attachments — images, documents, spreadsheets. A single MSG file with a large PDF attachment can easily exceed 10MB, 20MB, or more.
Most web-based converters enforce file size limits. Exceeding the limit produces either an upload error or a timeout after the file starts transferring.
What to do
Check what file size limit the converter you’re using imposes, and check the actual size of your MSG file (right-click → Properties on Windows, or Get Info on Mac).
If the file is over the limit and you need the email content but not the attachments, try saving the email in Outlook as a new MSG without the attachments: open the email in Outlook, delete the attachments, and use File → Save As to save the modified version as MSG. This gives you an MSG file that contains only the email body and headers — usually much smaller. The original (with attachments) remains in Outlook.
If you need the attachments too, the approach depends on the converter. Some converters handle large files better than others. If your current tool can’t handle the file size, try a desktop-based conversion tool rather than a web uploader — desktop tools don’t have the same upload size constraints. See the FAQ for current file size limits.
The File Is Corrupt or Incomplete
MSG files can be corrupted during save, transfer, or storage. Corruption can be subtle — the file opens in a file manager without errors but fails during conversion — or obvious, with the file refusing to open at all.
Common causes of MSG file corruption:
- Interrupted save: If Outlook crashed or the system shut down while saving an MSG file, the file may be written incompletely
- Storage failure: A failing hard drive or bad storage sector can corrupt file data
- Transfer error: Interrupted downloads, email attachment truncation, or transfer via a system that modifies binary files (FTP in ASCII mode, for instance) can corrupt MSG files
- File system issues: NTFS errors or problematic cloud sync can result in truncated or zero-length files
How to check if the file is corrupt
Try opening the MSG file directly in Outlook. If it fails to open, errors on load, or shows an empty/blank message, the file is likely corrupt. If it opens correctly in Outlook, the file itself is probably fine and the conversion failure has a different cause.
What to do
If the file is corrupt, your recovery options depend on whether you have a backup. Check:
- Whether the original email is still in Outlook — if so, save a fresh MSG copy
- Whether you have a backup copy of the file from before it was corrupted
- Whether the file was emailed to you — in which case the sender’s copy is intact
If the file is partially readable, some MSG repair tools can recover content from partially-corrupt MSG files. These are specialized utilities and results vary. For files where only partial recovery is possible, note what content you were able to recover and what was lost.
The Wrong File Extension
Not every file ending in .msg is actually an MSG file. MSG is sometimes used as an extension for other file types — most commonly Windows error report files (also .msg) or Winmail.dat-derived files that have been renamed.
A converter built for Outlook MSG files will fail if it receives a file that uses .msg but has a different underlying format.
How to check
Try opening the file in a text editor (Notepad on Windows, TextEdit on Mac in plain text mode). A genuine MSG file will show binary content — a mix of recognizable text and binary characters. If the file opens as readable plain text, it’s not an MSG file regardless of the extension.
A Winmail.dat file (which Microsoft Exchange sometimes uses to wrap attachments) contains TNEF-encoded data and can contain MSG-like content but requires a TNEF decoder, not an MSG converter.
What to do
Identify what the file actually is and use the right tool for it. If you received the file as an email attachment, check what the sender said it was. If it’s a TNEF/Winmail.dat file, use a TNEF decoder to extract the content. If it’s an EML file with a wrong extension, rename it to .eml and use the EML to PDF converter instead.
Character Encoding Issues
MSG files from older versions of Outlook, or emails received from certain international senders, may contain text encoded in non-Unicode character sets — ISO-8859-1, Windows-1252, Shift-JIS for Japanese content, GB2312 for Chinese, and others. If the converter doesn’t correctly identify and handle the encoding, the resulting PDF may show garbled text, question marks, or boxes where characters should be.
What causes this
MSG files store text in the character set that was active when the email was created or saved. Very old Outlook versions default to ANSI character sets rather than Unicode. Emails from legacy systems or non-English-language email clients may use regional encodings.
What to do
If the PDF output has garbled text but the conversion itself “succeeded” (you got a file back), the issue is encoding. Try opening the original MSG in Outlook to see if Outlook displays the text correctly — if it does, Outlook is correctly interpreting the encoding, which gives you a fallback: use Outlook’s File → Save As → PDF (in Outlook 2016+) or print-to-PDF from within Outlook, which lets Outlook’s own rendering handle the encoding. The output may have slightly less complete headers than a dedicated converter, but the text content will be correctly rendered.
The MSG File Contains Encrypted or S/MIME-Signed Content
If the email was sent with S/MIME encryption or signed with a digital certificate, the MSG file may contain encrypted or signed content that can’t be read without the appropriate certificate.
Encrypted emails are intentionally unreadable without the recipient’s private key. An MSG converter operating on the file without that key can only see the encrypted payload, not the message content — resulting in a PDF that shows the encryption wrapper but no readable body.
Signed (but not encrypted) emails are different: the content is readable, but the signature block may cause confusion for some converters.
What to do
For encrypted emails, you need to decrypt the message first. This typically means opening the MSG in Outlook with access to the recipient’s certificate (if you’re the recipient, you should have the certificate installed), then re-saving the email as MSG after Outlook has decrypted it. The re-saved file will contain the decrypted content and can be converted normally.
For signed emails, most converters handle them without issue. If you’re seeing conversion failures on signed emails, try opening in Outlook and re-saving as MSG to create a clean copy without the S/MIME wrapper.
The MSG File Has Embedded Objects or ActiveX Controls
Old-style Outlook emails sometimes contain OLE-embedded objects — spreadsheets, charts, or other embedded content created with Office applications. ActiveX controls were used in some HTML-formatted emails in older Outlook versions. Converters can’t render these objects and may fail or produce incomplete output when they encounter them.
What to do
If the embedded content is critical, open the email in Outlook and double-click the embedded object to open it in its native application (Excel, Word, etc.), then save it separately. For the email itself, print to PDF from within Outlook — Outlook’s own print function handles embedded objects better than external converters, though it may show a placeholder rather than the embedded content.
Upload Interruption or Browser Issue
Sometimes the issue isn’t the file at all — it’s the upload. A network interruption mid-upload, a browser tab that went to sleep, or a session timeout can cause failures that look like conversion errors but are actually transfer errors.
What to do
- Try refreshing the page and uploading again
- Try a different browser (Chrome is generally most reliable for file uploads)
- If on a cellular connection, switch to WiFi — large MSG files with attachments can take time to upload
- Try a smaller file to confirm the converter is working, then retry your original file
EML files: Some of these same issues apply to EML files. If you have an EML file that won’t convert, the same diagnostic approach applies — check file size, check whether the file opens correctly in a mail client, check for encoding issues. The EML to PDF converter handles standard EML files; if yours is failing, the troubleshooting steps above are a good starting point.
Quick Diagnostic Checklist
- File won’t upload: Check file size against the converter’s limit. Large attachments inflate MSG file sizes significantly.
- Upload succeeds but conversion fails: Try opening the file in Outlook. If Outlook can’t open it either, the file is likely corrupt.
- PDF is empty or has no email content: Check if the file extension is correct. Not every .msg file is an Outlook MSG file.
- PDF text is garbled: Encoding issue. Try converting via Outlook’s own print-to-PDF as a fallback.
- PDF shows encryption notice instead of content: The email is encrypted. Decrypt in Outlook first, then re-save and convert.
- Conversion works on other files but not this specific one: The specific file likely has a structural issue (corrupt, unusual format, embedded objects). Try opening it in Outlook and re-saving as MSG to create a clean copy.
More specific troubleshooting scenarios are covered in the FAQ. For bulk conversions where a subset of files fails, the bulk converter reports which files succeeded and which failed so you can isolate the problem files and investigate them individually.
Having trouble with a specific MSG file? Try the converter — most files that appear broken will convert correctly with the right tool.Try Converting Your MSG File →