What Is MailShift?
MailShift converts email files between formats that rarely play nicely together. EML to PDF. MBOX to individual EML files. MSG to HTML. VCF contact cards to CSV spreadsheets. If you have ever tried to open a Outlook .msg file on a Mac, or needed to archive a decade of Thunderbird emails as searchable PDFs, you already know why this tool exists.
Under the hood, MailShift includes a full MIME parser for EML and MBOX files, an OLE2 compound document decoder for Microsoft MSG files, and a vCard parser for VCF contacts. These are not trivial formats. MSG files in particular use the same binary container format as old Word documents, and parsing them correctly in pure JavaScript without a server is something most tools simply do not attempt. MailShift does it in your browser tab.
How to Use MailShift
Drop a file onto the upload area or click to browse. MailShift detects the format automatically, shows you a preview of the contents, and presents the available output formats. Pick one, click Convert, and the result downloads to your device. For MBOX files containing multiple messages, the tool splits them and lets you download them individually or as a single ZIP archive.
The conversion matrix on this page shows every supported input-to-output combination at a glance. Not every format converts to every other format -- some combinations do not make logical sense (you would not convert a VCF contact into an MBOX mailbox, for instance). But the paths that matter for real-world workflows are all covered. EML and MBOX files give you the widest range of output options since they contain the richest data.
Your Emails Stay Private
This matters more here than almost anywhere else. Email files contain sensitive information -- conversations, attachments, contact details, internal correspondence. MailShift processes everything locally in your browser using JavaScript. Your files are never uploaded to any server. There is no backend. The file you drop in and the file you download out both exist only on your machine. Once you close the tab, the data is released from memory entirely.
Common Questions
Can MailShift handle PST files from Outlook?
Not directly. PST is a proprietary Microsoft database format that is extremely complex to parse in a browser. However, you can export individual emails from Outlook as .eml or .msg files first, then convert those with MailShift. Many users export their PST to MBOX using a desktop tool, then use MailShift for the final conversion step.
Are email attachments preserved during conversion?
It depends on the output format. Converting to HTML or PDF preserves the email body and metadata. Attachments are referenced but not embedded in plain text output. When converting EML to MBOX or vice versa, the full MIME structure including attachments is preserved intact.
Is there a file size limit?
There is no hard limit imposed by MailShift, but your browser has memory constraints. Files up to about 100 MB typically process without issues on modern devices. Very large MBOX archives with thousands of messages may take longer and use more RAM. If your browser tab crashes, try splitting the MBOX into smaller files first.
Will email attachments be preserved during conversion?
Yes. When you convert an EML or MSG file to PDF, attachments are listed at the end of the document with their filenames and sizes. If you export to ZIP, each attachment is extracted as a separate file alongside the email body (saved as HTML or TXT). MBOX files can contain hundreds of emails — each one's attachments are handled individually. The parser reads the full MIME structure, so even inline images (those embedded in the email body rather than attached) are extracted correctly.
Can I search through thousands of emails in an MBOX?
The tool parses the archive and lists each email with sender, subject, and date. Select specific emails to export. Large archives (10,000+) may take a minute or two.
What's the difference between EML and MSG?
EML is plain-text format (Thunderbird, Apple Mail). MSG is Outlook's proprietary binary format. Both contain the same info but structured differently. This tool reads and converts between them.
Can I extract just attachments without email text?
Yes, ZIP export extracts each attachment as a separate file. Inline images embedded in the email body are also extracted alongside regular attachments.
Do the converted emails preserve the original formatting (bold, italic, colors)?
EML and MSG files store email bodies as styled markup, so formatting like bold text, colored fonts, bullet lists, and embedded images are all preserved when converting to PDF or styled output. Plain text export strips formatting by design, giving you the raw message content. If someone sent you a nicely formatted newsletter or styled corporate email, the PDF output captures it exactly as it looked in their email client.