EML to MBOX

This tool bundles one or more EML email files into a single MBOX archive. Every message is written verbatim, preserving all headers, body parts, attachments and inline images exactly as they were received when the archive is imported into a mail client. ⚠️ Only the mboxrd dialect is generated; other mbox variants are outside the tool’s scope.

Lossless email packaging

Every .eml you provide is written into the output .mbox without any alteration. All header fields, including custom X‑headers, the Message‑Id, and the exact line breaks are copied verbatim. The raw MIME body, whether plain‑text, HTML, or multipart, is stored unchanged, so the original structure and encoding survive intact when the archive is imported.

The archive uses the mboxrd dialect, placing a “From ” separator before each message that embeds the original sender address and the message’s timestamp in the traditional “Day Mon DD HH:MM:SS YYYY” format. This separator is recognized by the majority of desktop and command‑line mail programs, allowing seamless sorting, threading, and display of the bundled messages.

Attachments and inline resources stay intact

Binary attachments are kept in their original base64‑encoded representation inside the .mbox. When the file is opened in clients such as Thunderbird or Apple Mail, each attachment reappears with the same filename, size, and content type, enabling you to open, save, or forward it exactly as it was attached to the source email.

Embedded images that were referenced with a Content‑ID in the original email are preserved as inline parts, so the receiving client can render them directly within the message body without extra download steps. URLs pointing to external images are not fetched during packaging; they remain as the original HTTP(S) links, letting the client decide whether to load them according to its security settings.

Calendar invites and other special parts

iCalendar (.ics) components included in the source messages are written into the .mbox unchanged. Mail programs that understand calendar invitations will present them as actionable events, allowing you to add the meeting to your calendar directly from the imported message, while clients that treat them as generic attachments still expose the original .ics file.

Any non‑standard or proprietary MIME parts – such as encrypted blobs, custom application data, or experimental content types – are also carried through without modification. This guarantees that the archive remains a faithful container for the full spectrum of data that the original emails carried, ensuring future tools can interpret or extract those parts if needed.

Limits and scope

Batch size

Accepts any number of .eml files in one submission, constrained by the upload size limit of the current account tier.

Output retention

Generates one output.mbox file that can be downloaded for 24 hours after the conversion completes.