1. A method, comprising the computer-implemented steps of: receiving an electronic mail message that comprises one or more hyperlinks; determining sender information that identifies a sender of the electronic mail message; creating and storing a record that associates the sender information with each of the one or more hyperlinks; receiving a request to access a specified hyperlink among the one or more hyperlinks; retrieving, based on the specified hyperlink, the record; retrieving, based on the sender information associated with the specified hyperlink, sender reputation information associated with the sender; determining, based on the sender reputation information, a particular action among a plurality of allowed actions; issuing a network request to access the specified hyperlink only when the particular action is allowing user access to the specified hyperlink.
4. A method as recited in claim 1 , wherein the request to access the specified hyperlink is received at an HTTP proxy, and wherein the electronic mail message is received at an SMTP mail transfer agent that is coupled to the HTTP proxy.