I know this suggestion has been made before, probably by myself, but it seems the remailer programmers may be missing a good opportunity in not pursuing the inclusion of remailer code in the popular Gnutella cleints (e.g., LimeWire). They advertise they are looking for new "content communities." http://www.limewire.com/index.jsp/formgroup I don't see any reason why email can't be added as a new form of content.
Remailers are trickier than other P2P applications because of the problem of sending the mail out. If one of the P2P users gets "volunteered" to be the outgoing portal for some harrasing mail, he won't be running the client for long. However if the recipients are restricted to users of the P2P network then this is not a problem. An anonymous email application just for P2P users would be interesting. It could be part of a continuum of applications like anonymous chat with varying degrees of real-time delivery. KNet, knet.sourceforge.net, is a new project on P2P anonymous chat. If that works, then email could be done by adding some kind of queueing feature which would hold messages for delivery until the recipient connects to the P2P network. There wouldn't be many problems with complaints about abuse because everyone would be volunteering to receive anonymous mail/chat by virtue of using the network. Probably the biggest complaint people would have is untraceable spam. It's already a nuisance with other chat systems. If the anonymous comm system has per-user traffic limits or some other way of handling spam then it could be a good basis for no holds barred discussions and data exchange.