How to Export Outlook Email to .eml or .mbox Format

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What are .PST and .MBOX files?

Pst files and Mbox files both email messages.  While PST files proprietary to Microsoft Outlook, Mbox is an open specification used by email clients such as Mozilla Thunderbird.  RFC-822 and subsequently RFC-2822 are the open specifications documents that describe internet messaging and embody the structure of .eml files.   An MBOX file is a “mailbox” file which contains a collection of RFC-2822 email.  So .MSG is to .EML what .PST is to .MBOX.

RFC-822 was not directly adopted by Microsoft Outlook, the leading email client software in the world. Outlook email messages are stored in a single .PST file which may contain thousands of individual emails, messages including their file attachments. The specification for  creating a .pst file is proprietary, and is determined by Microsoft Corporation. The .pst specification was closed until Microsoft began publishing parts of the specification in 2010.
When Outlook exports a single email item from a .pst file, it is saved as a .msg file, which is also a proprietary Microsoft specification. Outlook .msg and .pst files requires Microsoft Outlook, or an Outlook viewer such as PST Viewer Pro.
Emails within a .mbox mailbox are concatenated and stored as in plain text. The start of a message within the .mbox file is delineated by a line with the word “From” followed by a space and the return path e-mail address.
Because RFC-822/2822 is an open specification it has been adopted by email client software such as Mozilla Thunderbird. It is still used to store and exchange email messages. Some companies prefer to store emails in this open standard, rather than in a proprietary standard.

Exporting Outlook to .EML/.MBOX

Microsoft Outlook does not directly support exporting email messages from a .pst or .msg files to .mbox or .eml files. To do this requires a third party add-in extension to Microsoft Outlook.
MessageExport is a useful add-in for Microsoft Outlook for exporting email messages to formats that missing from Outlook. MessageExport integrates tightly with Outlook’s main toolbar to allow users to select email messages from within Outlook and then export the emails directly to .eml or .mbox format.
Choosing the "Export to .eml" email export function.
Export to .EML from Outlook toolbar
In addition to .eml and .mbox, MessageExport also adds other export formats to Outlook, such as .pdf, .msg, mhtml, gif, tif, text, html, and many others.
Image shows dozens of email export operations that can be performed by MessageExport add-in for MS Outlook.
Export formats included with MessageExport
To export Outlook emails to PDF with MessageExport, click a message or messages in the Outlook message list so that they are highlighted. Next, select the export format from the MessageExport dropdown list (.eml or .mbox) and then click the Export button.  MessageExport may ask you to select a target folder, and once done will begin to export the selected emails.
If you export to .mbox, then all of your selected Outlook emails will be in a single .mbox file.
If you export to .eml, then you will have one .eml file for each Outlook email that was selected.
MessageExport also includes a “drag and drop” conversion capability.  Using MessageExport’s Export Folder Explorer, you can immediately convert a message to the selected format just by dragging that file and dropping on a folder in the explorer.
Drag and drop email conversion from MS Outlook.
Export folder explorer in closed state, resides on the right-hand side of the Outlook window. To use it, click to expand.
Selecting the appropriate folder for despositing email that has been converted.
Export folder explorer in expanded state.  Drag and drop email messages on the selected folder to immediately convert it to the currently selected format.
 MessageExport is a useful add-in for convert Outlook email message to .eml, .mbox, .pdf and other formats that are not natively included with Microsoft Outlook.  You can download a free 15 day trial of MessageExport.

Viewer makes it easy to open .EML files on iPad

iPad screen shot.
Apple iPad users who depend on email may sometimes have a need to open .msg and .eml files. Sometimes email files types come as attachments in email messages.

We decided to try Klammer, the email file viewer app from Kupon B.G. that is available in Apple’s App Store. Klammer says it will open Outlook .msg files, standard .eml files, and also winmail.dat files on your iPad. We purchased the app and took it for a spin on our iPad, testing its ability to open both eml and Outlook msg files.

To test Klammer,  we sent ourselves an email message containing a plethora of .eml and .msg files as attachments.

First we opened our email using the iPad’s Mail application.  The file attachments were immediately visible in the email.

Eml files shown in Klammer app.
EML Files attached to our email message

To view the file attachments in Klammer, we simply touched the .eml file we wanted to view, pressing on it for a full two seconds.  iPad then opened a window asking us which application we wanted to use to open the file.  We choose Klammer.

Image shows Klammer icon in IOS.
Klammer app in IOS.

The .eml file immediately appeared rendered in full html formatting. Below is the result when we opened a promotional .eml file attachment in Klammer.


.eml file opened on iPad device.
EML file opened on iPad

In our tests, Klammer performed very well. We opened .msg files, .eml files, both with a mixture of text, and html formatting.  It opened every email we gave it without losing the formatting.

There’s not a lot of bells and whistles with Klammer. It does what it says: no more, and no less.

Klammer is a very simple app for opening .msg and .eml email messages. It integrates logically within IOS.

When you first acquire Klammer, the cost is .99 cents. This allows you to open .eml files only. If you want to add .msg file capabilities to Klammer, the cost is an additional $1.99.  Despite the publisher’s statement to the contrary, some users people get confused about this, thinking that both file types are part of the 99 cent purchase.

If you are an iPad or iPhone users who need an easy way to open individual .eml or .msg files, Klammer is well worth the $2.99 investment.

You can learn more about Klammer in the Apple App Store.

Image of Klammer app's about page.
Klammer app’s About page