Open MSO File

File extension MSO is most commonly associated with an inline E-Mail attachment sent via Microsoft Word 2000, and contains information required to display the attached file within the E-Mail message. Though less common, an MSO file may also refer to a Microsoft Office macro reference file, a MathScript object or a MedleySound Module.

When an HTML E-Mail is composed which contains an inline Microsoft Word 2000 attachment, an additional file called Oledata.MSO is created which contains the information required to render the attachment in its original application. If the recipient opens the E-Mail in Microsoft Outlook, the additional MSO attachment is not seen, the E-Mail message displays correctly and any Microsoft Office attachments can be viewed correctly in the application they were created in. However, if the recipient is using an alternative E-Mail client which is not compatible with Outlook HTML E-Mails they will see the Oledata.MSO file as an additional attachment. Though MSO files can be opened using any text viewer, they are encoded so cannot be understood or edited and contain no information of use to the user. Additionally, modifying the contents of the file or deleting it may render the attached Microsoft Word document unusable so should not be removed.

Microsoft Office macro reference files also use the MSO file extension, and are created when documents created in Microsoft Office are saved as web pages to store links to macros and other embedded objects. These are also encoded and contain no information of use to the user, so should not be opened manually.

MSO files which represent inline E-Mail attachments can only be opened using Microsoft Outlook 2000 or later or any other E-Mail client which is compatible with embedded Office document attachments. MSO files which are produced by MathScript and MedleySound can only be opened successfully in their intended application.