Providing version control for electronic mail attachments

A system for providing version control for documents attached to electronic mail messages in which a user's personal document library is used to store documents attached to the email messages the user sends and/or receives. Each time an attached document is transmitted or received within a message thread, a different version of the document is created and stored in the personal document library. The multiple document versions created allow the disclosed system to provide the user with the options of opening the most recent version of an attached document and/or opening the version of the attached document that is associated with the specific opened message. An attached document is represented within an email message using a URL (Uniform Resource Locator), where the stored URL points to the version of the attached document for that message that is stored in the user's personal document library. Through an API (Application Programming Interface) provided by the personal document library, the most recent version of a document can be requested, or another specific version of the document can be indicated for opening.