EML vs PST: Understanding their Differences and Uses

Emails are stored in different file formats depending on the email client. The two popular email formats are EML and PST. If you have ever migrated from Thunderbird or Windows Live Mail to Outlook, or tried to open an Outlook email in another email client, there is a good chance that you have come across emails in EML and PST file formats. It is therefore vital to understand the difference between EML and PST file formats before planning email migration, backup, or conversion.

What is an EML File?

EML stands for Electronic Mail message format. It is a standard email file developed by Microsoft for Outlook Express and adopted by many other email clients. An EML file stores a single email along with attachments. This is essentially a text message file in the MIME RFC 822 standard.

EML File Structure

The typical structure of an EML file is as below:

• Header: Contains From, To, CC, Subject, Date, Message-ID
• Body: Text format and HTML version of email
• Attachments: Encrypted and Base64 encoded

Supported Email Clients

Email clients that use EML files include:

• Mozilla Thunderbird
• Microsoft Outlook
• Apple Mail
• The Bat!
• eM Client
• Mailbird
• Windows Live Mail or Outlook Express
• SeaMonkey

What is a PST File?

PST stands for Personal Storage Table file. It is a proprietary and encrypted file that stores complete mailbox information locally on your computer by Microsoft Outlook.

Compared to EML which stores a single email per file, a PST file can store thousands of emails, contacts, calendars, tasks, notes, journals, and the entire folder hierarchy.

There are mainly two types of PST files:

• ANSI PST: Older PST format used in Outlook 2002 and earlier versions, with size limitation of 2GB.
• UNICODE PST: It came with Outlook 2003 and has a size limit of 50GB (supports up to 1TB of data after expansion).

When Should You Convert PST to EML?

You may want to convert PST to EML in the following situations:

• Migrating from Outlook to Thunderbird

Since PST is Outlook specific, you will have to convert PST to EML to access Outlook emails in another email client like Thunderbird.

• Viewing PST without Outlook

If you don’t have Outlook installed, you can’t access or open the PST file. Converting PST to EML will let you open emails in free email clients and even browsers.

• Accessing individual email messages

If you need to share one email as an attachment, you can’t share a 20GB PST file. You will have to extract it and save it as a single EML file.

When Should You Convert EML to PST?

Take a look at the common scenarios when there may arise the need to convert EML to PST: 

• Migrate From Thunderbird/Windows Live Mail to Outlook

This is the most common situation where you need to convert EML to a PST file. If you have lots of email folders saved as EML and you want to move them to Outlook, it cannot be done directly.

• Consolidate For Backup

If you have 10,000+ EML files scattered across different email folders, it will be quite a task to back up and search. It would be wise to convert them into one organized PST file format to make your work easier.

• eDiscovery & Legal Compliance

Lawyers and compliance officers prefer PST files as they can be indexed and searched easily.

• Opening EML in Outlook

You can double-click on EML to open it in Outlook, but you can’t organize and categorize them in Outlook. Converting the EML files to PST lets you use all Outlook features for managing emails.

Which Format Should You Use: EML or PST?

Use EML format when you are likely to need portability and want to share individual messages. EML files are easily accessible in cross-platform email clients like Thunderbird, Apple Mail, Windows Live Mail, etc. This makes it a great choice for sharing one email as legal evidence or for archiving a few important email messages.

Use PST format when there is a need to manage thousands of emails in one file and want to retain folder structure, read/unread status, etc. It is ideal for full mailbox backups and migrations to Outlook or Office 365.

Conclusion Lines

PST and EML are two different file formats and they are designed for different email needs. EML is ideal for single email portability, and on the other hand, PST is ideal for complete mailbox backup/archive. There are different scenarios where users need to convert their EML files, and using Kernel for EML to PST Converter software can make that process easy.

Frequently Asked Questions

Q. Can Outlook open EML files directly?

Ans. Yes, Outlook can open EML files by double clicking it. However, you can’t bulk import EML files to Outlook manually.

Q. Which one is safer for long term archiving - EML or PST?

Ans. EML is safer, as corruption of EML files doesn’t affect others. But PST corruption can lead to the loss of thousands of emails.

Q. Can I convert EML files to PST format without Outlook manually?

Ans. No, manual methods require Outlook to convert EML files to PST format.