It is often possible to break the server system, perhaps over an SSL connection. All of these threats must be considered before selecting an SSL based security approach for any application. Secure E-mail Messaging is an end to end application where data is transferred between two users, typically using a store and forward mechanism. This means that SSL is particularly inappropriate to support secure e-mail, as it only offers protection over the link. Protection only exists where exchange is between users with accounts on the same e-mail server.
All protection is lost when messages are sent to other Internet users.
A Web interface must be used for e-mail. This is acceptable for low volume personal use, but is not a good option for a user that makes extensive use of e-mail, which is now normal in a corporate environment. A Web interface also integrates poorly with the desktop, which makes it awkward or impossible for exchanging secure documents, and generally to support business to business communication. SSL is really not a sensible choice for e-mail security. There is a class of e-commerce applications that can use either a Web based or messaging based approach.