My email address is adam@dunkels.com. I really like getting emails (particularly I like to hear how and where my software is used!), but get quite a large amount of email and at times I get so much that I cannot handle it all. I actually try to answer all, however. Sometimes it can take a long time, and sometimes I have to drop emails. Don't be offended if you don't get a reply.
For questions regarding the Contiki operating system, try the contiki-developers mailing list here.
For questions regarding the uIP embedded TCP/IP stack, try the uip-users mailing list here.
I am no longer active in the lwIP project. For questions regarding lwIP, try the lwip-users mailing list here.