The Problem: Outlook Does Not Open EML Files Natively
EML files are the standard format for individual email messages, widely used by Thunderbird, Apple Mail, and many other clients. However, if you are migrating to Microsoft Outlook or need to consolidate a large collection of EML files into a single archive, Outlook’s native support for EML is limited. While you can sometimes drag an EML file into Outlook, the process is unreliable for bulk imports and does not preserve folder structure.
IT professionals managing email migrations frequently face this challenge. A department switches from Thunderbird to Outlook, or archived emails stored as EML files need to be combined into a single PST for delivery to a client. Converting EML files to PST creates a clean, organized archive that Outlook opens directly.
Solution: Convert EML Files to PST With MailtoPst
MailtoPst reads your EML files and assembles them into a properly formatted PST file that Outlook recognizes immediately.
Step-by-Step Guide
- Gather your EML files — collect all the EML files you want to convert. They can be in a single directory or organized in subdirectories.
- Go to mailtopst.com/convert/eml-to-pst.
- Upload your EML files — you can select multiple files at once or upload a ZIP archive containing your EML collection. If you upload a ZIP, the folder structure inside it becomes the folder structure in the PST.
- Wait for processing — MailtoPst parses each EML file, validates its structure, and assembles the PST output.
- Download the PST file and open it directly in Microsoft Outlook via File, then Open & Export, then Open Outlook Data File.
What Gets Included
- All message headers (From, To, CC, BCC, Subject, Date).
- Full message body in plain text and HTML.
- All attachments embedded in the EML files.
- Folder structure based on the directory layout of your uploaded files.
- Original timestamps preserved in the PST.
Why MailtoPst for EML to PST
- Batch conversion — convert hundreds or thousands of EML files in a single operation. No need to import them one by one.
- Folder structure mapping — organize your EML files in folders before uploading, and that structure carries into the PST.
- Standards-compliant output — the PST file follows the MS-PST specification and opens in all versions of Outlook (2010, 2013, 2016, 2019, 2021, Microsoft 365).
- Secure processing — files are encrypted via TLS in transit, processed on EU-based servers, and auto-deleted after conversion. Fully GDPR compliant.
- No software required — the entire conversion runs in your browser.
Try free — no credit card required. Upload your EML files and get 100 MB of free conversion credit.
Common Use Cases
Migrating From Thunderbird to Outlook
Thunderbird stores emails in MBOX format but can export individual messages as EML. Export your Thunderbird emails as EML files, then convert them to PST with MailtoPst for a clean import into Outlook.
Consolidating Email Archives
If you have years of email saved as individual EML files across multiple folders, converting them to a single PST creates a compact, searchable archive that Outlook can manage efficiently.
Legal and Compliance Delivery
Law firms and compliance teams often receive email evidence as EML files. Converting to PST makes it easier to load the data into Outlook-based review platforms or deliver it to clients who use Outlook.
Backing Up Cloud Email
Many cloud email services allow you to download messages as EML. Converting these to PST gives you a single-file backup that is easy to store and restore into Outlook if needed.
Frequently Asked Questions
Can I convert thousands of EML files at once?
Yes. Upload a ZIP archive containing all your EML files. MailtoPst processes the entire batch and produces a single PST output. There is no limit on the number of messages — only on total file size (up to 50 GB on the Enterprise plan).
Will the conversion preserve email attachments?
Yes. All attachments embedded in the EML files are included in the resulting PST file. Attachment types, filenames, and sizes are preserved.
Can I choose which Outlook version the PST targets?
MailtoPst generates Unicode PST files (ANSI PST is obsolete since Outlook 2003). Unicode PST files are compatible with Outlook 2010 and all later versions.
What if some of my EML files are malformed?
MailtoPst is tolerant of minor formatting issues in EML files. Messages that cannot be parsed are skipped, and a report lists any files that failed. The rest of the conversion completes normally.
Can I also convert MBOX files to PST?
Yes. If your emails are in MBOX format rather than individual EML files, use the MBOX to PST conversion instead.
Upload your file now and bring your EML emails into Outlook.