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How to Convert EML Files to PDF in Bulk

Convert many EML files to one sorted PDF in bulk. Keep attachments with each email, sort by sent date, and catalog the whole set with a CSV index.

Loose EML files pile up fast. You may have ten on your desktop. You may have ten thousand in an old folder. Each one holds just one email, all on its own.

This guide shows you how to gather them into one PDF. The PDF sorts the mail by its true sent date. It keeps each attachment with the right email. It also gives you an index you can search and sort.

You can convert EML files in bulk with MBoxToPDF in your browser. You drag in many files at once. The tool builds one merged volume for you. The steps below show the full job from start to end.

What an EML file is

An EML file holds one single email. It holds the text of that email. It holds the facts about that email too. It may also hold files that were sent with it.

EML is a plain, open format. Plain means the file is mostly simple text. Many mail apps can read it with ease. That is why it has lasted for so long.

Thunderbird can save a mail as an EML file. Apple Mail can do the same on a Mac. Long ago, Outlook Express used this format a lot.

Loose EML files also show up in legal work. In e-discovery, staff collect emails one by one. E-discovery is the search for facts in stored files.

How you get a pile of loose files

You may drag mail out of an app, one by one. A past job may have left you a shared drive full of them. A client may send you a folder of saved emails. The files often have short, odd names that tell you little.

File names are a weak guide to what is inside. A name may show a date that is wrong. It may show no date at all. The real facts sit inside the file, not in its name.

EML, MBOX, and MSG side by side

Three formats cause most of the mix-ups. They all hold email, but in unlike ways. The table below shows how they differ. Read it before you pick a tool for your files.

The key split is simple to state. EML holds one message in each file. MBOX holds many messages in one file. Both are plain formats that many tools can read.

MSG is the Outlook format for one message. It stores the mail in a way that suits Outlook. If your files are MSG, you can convert Outlook MSG files instead with the same steps.

MBoxToPDF reads all three formats in one job. You can mix EML, MBOX, and MSG files together. They all land in one merged PDF volume. That helps when a set comes from more than one source.

One limit is worth a clear note here. MBoxToPDF does not open PST files directly. A PST file is a big Outlook store file. Export it to one of the three formats first.

Why loose files need one volume

A folder of loose files is hard to read as a story. You open one file, read it, and close it. Then you open the next one and start again. The thread of the talk gets lost fast.

One merged PDF fixes that at once. All the mail sits in one file, in order. You scroll through it like a book. You search the whole set with one search.

Each page says Page x of y at the bottom. A reader can cite an exact page with ease. Others can turn to that page and check the quote.

Why people keep old emails at all

Old emails are often real business records. They can back up a tax return, for one thing. The tax office in the US is the Internal Revenue Service, or IRS. Its rules say you must keep records while they may be material. Material means they could still affect your tax.

The IRS gives time frames for how long records matter. The general time to assess tax is three years. It is six years for a large understatement of income. Employment tax records must be kept at least four years.

Rules like these are one reason people keep mail in a firm form. A PDF volume is easy to store and share. It looks the same years later on most devices. The IRS note at the end of this guide has more detail.

How to convert EML files in bulk

The job is short and the steps are plain. You do not need to open each file first. You do not need to rename the files at all. Just follow these steps in order.

1. Gather your EML files in one folder.
2. Open the converter page in your browser.
3. Drag in all the files at once.
4. Choose date order or group by thread.
5. Start the conversion and wait for it to end.
6. Download the merged PDF and the extras.
7. Open the PDF and check a few pages.

A thread is a chain of emails on one topic. It holds the first mail and all the replies to it. Grouping by thread keeps each talk in one block. Date order puts the oldest mail first across the set.

Sorting by the real sent date

The tool reads the date inside each file. That date is the date the mail was sent. It is not the date the file was saved. It is not the date you copied the folder.

Saved files often carry the wrong date on the outside. A copy made last week looks brand new. But the mail inside may be five years old.

The volume sorts by the true date, oldest first. So the story reads in the order it happened. Replies land after the mail they reply to.

A few old files may have no date inside. The tool puts those at the end of the volume. They stay in the same order as you gave them. They are still in the PDF in full.

What the volume contains

The merged PDF is built like a small book. It starts with a cover page. Then it has a table of contents. The contents list names each email and its start page.

Each email starts with a header block. A header block is the set of facts at the top. It shows who sent the mail and when. It shows these six facts for each email.

• From, which names the sender of the email.
• To, which names the main person it went to.
• Cc, which names others who got a copy.
• Date, which shows when the email was sent.
• Subject, which is the title of the email.
• Message-ID, which is a unique code for that email.

The Message-ID helps you match files across sets. No two emails share the same code. If the same mail shows up twice, the code shows it. That is a fast way to spot a true duplicate.

Keeping attachments with the right email

Loose files raise a real fear for most people. Will the photo stay with the mail that sent it? Will the signed form land next to the right note?

The tool keeps each attachment tied to its email. An attachment is a file sent along with an email. It is part of that email from the start. The volume treats it that way throughout the job.

Some attachments also become pages in the PDF. PDF files become pages right after their email. Images become pages right after their email too. Plain text files become pages as well.

Every attachment is also saved inside the PDF. It is kept as its first, original file. A reader can open the true file from the PDF. They do not get a flat picture in its place.

Word, Excel, and PowerPoint files do not become pages. They are listed with the email they came with. They are saved inside the PDF as files. On paid plans they also go in the ZIP file.

A ZIP file is a packed file you can download. On paid plans it holds one PDF per email. It also holds the attachment files in full. A single attachment over 25 MB is not saved inside the PDF. It is still in the ZIP and noted in the index.

To learn more about this part of the job, read how to keep attachments with their emails in a merged volume.

The CSV index as a catalogue

A loose set needs a list you can search. Starter and Pro plans give you that list. It is a metadata CSV index file. Metadata means facts about each email, not the text itself.

A CSV file is a simple table of rows and columns. You can open it in a sheet app like Excel. You can sort it, filter it, and search it. That makes it a true catalogue of your whole set.

The index has one row for each email. Each row holds the key facts for that mail. Here is what each row lists for you.

• The date the email was sent.
• The sender and who the mail went to.
• Who got a copy of the email.
• The subject line of the email.
• The names of any attachments.
• The message code for the email.
• The thread code for its talk chain.

The index also flags mail that had a problem. Some old messages are corrupt, which means damaged. Some are encrypted, which means locked with a key. Those mails are flagged in the index, not dropped in silence.

Filters and Bates numbers on Pro

Pro adds two tools that help with big sets. You can filter mail by date range before export. You can also filter by keyword before export. The keyword is matched in the subject, sender, and body.

Pro also adds Bates numbering for formal sets. Bates numbering stamps a code on each page. You set the prefix and the first number. The stamp runs across the whole volume in order.

The stamp sits in the footer of each page. It runs through the cover and contents pages too. The cover page prints the full Bates range. The CSV notes the first and last Bates number for each email. Those columns are called bates_start and bates_end.

Plans and limits

Each plan has a file size limit. Each plan also has a mail count limit. Only a good conversion counts toward your monthly total. A failed job does not use up your allowance.

You can see what each plan includes in full on the pricing page. The short table below shows the key limits. Use it to match your set to the right plan.

The Free plan gives you the merged PDF only. It suits a small test or a small set of files. Starter and Pro add the CSV index and the ZIP. Pro adds filters and Bates numbering on top of that.

Common problems with loose files

Bulk jobs meet the same few problems most times. Each one has a plain cause and a plain fix. Here are the ones people ask about most.

The same email shows up twice

Old sets often hold the same mail more than once. It may sit in two folders with two names. The Message-ID in each header block gives it away. Check the codes in the CSV index to find pairs.

File names tell you nothing

Names like mail1 or note-final say very little. Do not sort or trust the files by name. Let the tool read the facts inside each file. That is the whole point of a bulk conversion.

One file will not convert

One bad file does not spoil the whole job. The rest of the set still converts as normal. The bad file is flagged in the CSV index. You can then look at that one file on its own.

How your files are handled

Your files travel over HTTPS, a safe link. HTTPS scrambles data while it moves online. The files are then processed on the server. Processing just means the conversion work itself.

Files are deleted on their own after 24 hours. You do not need to ask for this. The service does not read mail for other uses. It does not sell data or train models on your mail.

Download your results soon after the job ends. Save the PDF and the index in one place. Then you hold the copy that lasts for years.

A quick final check

Open the volume and read the cover page first. Then use the contents list to jump around. Check one mail with an attachment in the set. Make sure its pages sit right after that mail.

Search the PDF for a word you know is there. Then open the CSV index in your sheet app. Sort it by date and by sender once each. If both files look right, your bulk job is done.

Your loose files are now one sorted volume. It reads in true date order from start to end. It has a catalogue you can search in seconds.

References

• Internal Revenue Service — Topic No. 305, Recordkeeping