1. A computer-implemented method of providing version control for documents attached to electronic mail messages, comprising: detecting a transmit message operation resulting in a transmitted electronic mail message being stored in a sent items folder of messages, said transmitted message having an attached document and belonging to a message thread; determining, in response to said detecting of said transmit message operation resulting in said transmitted message being stored in said sent items folder of messages, whether a version of said attached document was previously stored in association with said message thread to which said transmitted message belongs in a personal document library of a local user; in response to determining that said previous version of said attached document is stored in said personal document library in association with said message thread to which said transmitted message belongs, determining whether said attached document has been modified since said previous version of said attached document was previously stored in said personal document library in association with said message thread to which said transmitted message belongs; and in response to determining that said attached document has been modified since said version of said attached document was previously stored in said personal document library in association with said message thread to which said transmitted message belongs, creating a new version of said attached document by storing said attached document into said personal document library in association with said message thread to which said transmitted message belongs; and responsive to said local user selecting a user interface object indicating said attached document in an electronic mail message user interface enabling said local user to perform actions regarding said transmitted message, presenting a document open user interface including multiple document open options, wherein a first of said document open options enables said local user to open said new version of said attached document, and wherein a second of said document open options enables said local user to open a most recent version of said attached document contained within said message thread, wherein said most recent version of said document was previously received as an attachment to an electronic mail message in said message thread received subsequently to said transmitted message, and wherein said document open user interface further enables said local user to make said new version of said attached document said most recent version of said attached document in said message thread by assigning a new highest version number to said new version of said attached document.
2. The method of claim 1 , further comprising storing a pointer to said new version of said attached document in said detected message.