Microsoft Office Macro Reference File
3.3 | 131 Votes
What is an MSO file?
An MSO file is a macro reference file created when saving a Microsoft Office document as a webpage. It contains information about macros and OLE (Object Linking and Embedding) objects included in the original file and may be referenced by the created webpage as a style sheet. MSO files may be viewed with a text editor, but will be unreadable since the contents are encoded.
Most users will only see the MSO file as an attachment to an email. Do not open the file if it has the ".mso" extension because it most likely contains a virus that will be installed on your computer when opened.
Programs that open or reference MSO files
Outlook In-Line Office Attachment
2.7 | 39 Votes
Oledata.mso is an email attachment automatically created by Microsoft Outlook. Outlook automatically adds oledata.mso to emails that contain an attached Office document. When another Outlook user receives an email that contains oledata.mso, they can view the attached Office document as part of the email itself.
Desktop Outlook users never see oledata.mso. Instead, they see only the attached Office document, displayed as both an attachment and within the email itself. (In the web version of Outlook, users can see attached oledata.mso files.)
In non-Outlook email programs, oledata.mso appears as a separate attachment, and the attached Office document does not appear as part of the email. Instead, the document appears only as a normal attachment.
In some cases, email programs may automatically block recipients from receiving messages that contain oledata.mso. These email programs regard oledata.mso as a potentially dangerous executable file, and thus do not allow users to view or open messages that contain the file.
Common MSO Filenames
Oledata.mso - The name Microsoft Outlook assigns to all MSO files.
How to open an MSO file
Oledata.mso is not meant to be opened. If you receive an email that contains oledata.mso, you can likely disregard oledata.mso and open the email and its other attachments as you would normally.