Can I Convert Multiple Email Files at Once?

The Problem: Converting Files One by One Is Slow

If you have a folder containing hundreds of EML files, a dozen PST archives from different users, or years of MBOX exports from Thunderbird, converting them individually would be tedious and time-consuming. You need a way to process multiple files in a single operation — commonly called batch or bulk conversion.

Solution: Batch Conversion With MailtoPst

MailtoPst supports batch conversion for all major email formats. The approach depends on the source format.

Batch Converting Multiple EML Files to PST

This is the most common batch scenario. You have hundreds or thousands of individual EML files and want them combined into a single PST archive.

1. Organize your EML files into folders that represent the structure you want in the PST (e.g., Inbox/, Sent/, Projects/2024/).
2. Create a ZIP archive containing all the EML files and their folder structure.
3. Upload the ZIP to mailtopst.com/convert/eml-to-pst.
4. Download the resulting PST file. The folder structure from the ZIP is preserved in the PST.

A single ZIP upload can contain thousands of EML files. MailtoPst processes them all in one operation.

Batch Converting Multiple EML Files to MBOX

Same process as above, but select EML to MBOX as the target. The output is a set of MBOX files, one per folder.

Converting a Large PST With Many Messages

If you have a single PST file containing thousands of messages, the conversion to EML or MBOX is inherently a batch operation — every message in the PST is extracted and converted. Upload the PST to PST to EML and receive a ZIP with all messages organized in folders.

Converting Multiple PST Files

If you have several PST files (e.g., one per year or one per department), convert each one separately. Each conversion produces its own output. You can then combine the results or keep them organized by source.

For organizations handling many PST files as part of a migration project, see the large-scale email conversion guide.

Tips for Efficient Batch Conversion

• Use ZIP for EML files — instead of uploading files one by one, bundle them into a ZIP. This reduces upload time and preserves folder structure.
• Organize before converting — set up your folder structure before zipping. The folder hierarchy in the ZIP becomes the folder hierarchy in the output.
• Check file sizes — the free tier supports up to 100 MB per conversion. For larger batches, a paid plan supports up to 50 GB.
• Name files clearly — while MailtoPst does not require specific naming, descriptive filenames help you verify the output.

Why MailtoPst for Batch Conversion

• Single-operation processing — upload once, get all results. No need to repeat the conversion for each file.
• Folder structure preservation — directory hierarchy in your ZIP is mapped to folders in the output PST or MBOX.
• High capacity — the Enterprise plan handles up to 50 GB of data, enough for archives containing hundreds of thousands of messages.
• Secure processing — all data is encrypted via TLS, processed on EU servers, and auto-deleted after conversion. GDPR compliant.
• No software needed — everything runs in your browser.

Try free — no credit card required. Upload your files now and get 100 MB of batch conversion credit.

Frequently Asked Questions

Is there a limit on the number of files in a ZIP?

There is no hard limit on file count. The constraint is the total size of the ZIP (up to 100 MB free, up to 50 GB paid). A ZIP with 50,000 small EML files is handled the same as one with 500 larger files.

Can I mix different file formats in one ZIP?

MailtoPst expects all files in a single conversion to be the same format. If you have a mix of EML and MSG files, separate them and run two conversions.

How long does batch conversion take?

Processing time scales with total data size, not file count. A 500 MB batch of 10,000 EML files typically converts in a few minutes. A 10 GB batch may take 15-30 minutes.

Can I convert multiple MBOX files to a single PST?

Currently, each MBOX file is converted separately. If you need to merge them into one PST, convert each to EML first, then combine all EML files into a single ZIP and convert to PST.

Will the email dates be preserved in batch conversion?

Yes. Every message retains its original sent and received timestamps, regardless of how many files are processed in the batch.

Upload your file now and convert all your emails in one go.