I am interested in information on what software small, medium, and large ISPs use for email services. When I refer to "email services" I mean SMTP, POP, IMAP, web mail interfaces, and the back-end administrative tools. Do many/most ISPs use big, expensive enterprise tools for this? Piece their own systems together using various commerical/free tools for the different parts? Or do they roll their own almost top to bottom? I have experience doing email for small and medium corporate sites (in the 100's of internal users), but the particular project I am working on is for customers, not internal users, and could quickly balloon from the few dozen on the current demonstration system to thousands. Any firsthand info or pointers to more information would be greatly appreciated. -- Crist J. Clark | cjclark@alum.mit.edu | cjclark@jhu.edu http://people.freebsd.org/~cjc/ | cjc@freebsd.org