Convert an email thread
to a single PDF.

An email thread — a chain, a trail, a conversation — is not one document. It is a series of separate messages that your mail client stitches together for display, usually by matching In-Reply-To and References headers or, in Gmail's case, by subject. When you "print the conversation" you get that stitched display: the quoted replies, in whatever order and trimming the client chose, with the headers of every message except the last one discarded.

That is fine for reading. It is a poor record. Each reply in a chain is its own email with its own sender, its own timestamp, and its own routing headers; the quoted text inside a later reply is just text the replier's client pasted in, and it can be edited before sending. If the trail matters — a dispute, a negotiation, an HR matter, a delivery timeline — you want each message preserved as itself, and then presented together in order.

Most clients let you download a message as an .eml file; the trick with threads is making sure you download each message individually rather than the collapsed conversation view. The export guide covers every major client in detail. The thread-specific notes:

1. Gmail (web). Expand the conversation so every message is visible. Use the three-dot menu on each message and choose Download message. The kebab at the top of the thread downloads only the message it belongs to, not the whole chain — one file per message is what you want. See Gmail export.
2. Outlook (desktop). Turn off conversation view (View → Show as Conversations) so each reply appears as its own row, select them all, and drag the selection to a folder. Outlook writes one .eml or .msg per message. See Outlook export.
3. Apple Mail and Thunderbird. Select all messages in the thread in the message list and drag them to a Finder or Explorer folder; each becomes its own .eml. See Apple Mail and Thunderbird.
4. Check the count. If the thread has twelve messages, you should have twelve files. Replies you sent yourself live in Sent; include them, or the trail will have gaps.

With the files exported, open the MailToPDF converter and drop the whole set in together. Everything happens inside the browser tab — the messages are parsed locally and never uploaded, so a confidential thread stays confidential.

1. Drop all the files at once. The converter accepts any number of .eml and .msg files in one batch.
2. Pick a header mode. Standard shows the essential headers for each message and reads cleanly. Forensic prints the complete raw header block for each message — choose this if the trail is evidence. Clean shows only the basics, for sharing or presentation.
3. Set the output to merged. Instead of one PDF per message, the converter produces a single PDF containing every message in the batch, one after another, with page numbers continuing across the whole document. A zip export is also available if you want the merged PDF plus every attachment in its original form.
4. Download. The merged file is named mailtopdf-merged.pdf; the SHA-256 of the merged PDF and of every source message is recorded so anyone can verify it later.

A merged thread is only useful if the reader can follow it. Three settings make the difference:

Order. Messages are placed in the order they appear in the file list, so sort the list by date before converting. Most exports are named after the subject, which is identical across a thread; if your client offers it, include the date in the filename, or simply add the files to the converter oldest first.

Bates numbering. Turn it on and the whole merged document gets sequential page identifiers (PREFIX000001, PREFIX000002 …), which makes citing "the reply at page 14" unambiguous in a filing, an audit, or a complaint. Prefix, padding and starting number are configurable.

Attachments. Threads accumulate attachments — a contract in message two, a revised version in message nine. The converter renders inline images in place, appends PDF attachments after the message they belong to, and lists every attachment with its size and hash in a manifest, so the version history is visible rather than lost.

Some organisations disable Print and Download in webmail through data-protection policies. Before working around it, check with your IT or compliance team: the block usually exists precisely so that email trails are not copied out of the system without a record, and there may be an approved export route (an eDiscovery hold, a compliance export, or a request to IT) that produces a better-preserved copy than anything you can do yourself.

Where export is permitted but the web interface is simply awkward, a desktop client connected over IMAP — Thunderbird is the easiest — will typically let you select an entire thread and save it as .eml files in one action, even when webmail won't. The Yahoo section of the export guide walks through the IMAP route.

Can I just print the Gmail conversation to PDF? You can, and for casual reading it is fine. But the result carries only the visible text: no per-message headers, no real timestamps for the earlier replies, no attachments, and quoted text that could have been edited before it was sent. For anything that might be questioned later, convert the individual messages instead.

Does the merged PDF keep each message's timestamps? Yes. Every message keeps its own Date header and, in Forensic mode, every Received line with its server timestamp and offset.

How many messages can I merge? There is no fixed limit — the work is done on your machine, so it is bounded by your computer's memory. Batches of several hundred messages are routine.

Can I convert a thread on my phone? Not well. Mobile mail apps generally cannot export .eml files; see the Gmail mobile note. Wait for a desktop.