I'd like to incorporate into my Website and I'll be forwarding these to colleagues as well. Email messages are subject to copyright law as well, since they are original works of authorship fixed in a tangible medium of expression. By either incorporating them into your Website or forwarding them on to colleagues without permission, you have probably committed copyright infringement. It would be best to get permission. On the other hand, those sending email can provide a note as part of their submission that either gives people permission to forward or use their message or advises them of copyright protection.
Many discussion lists have policies governing the forwarding and use of email messages.
Be aware of these before you post to a list. If you are sending email containing original material that you want to protect, make a print copy and date it. I think I've twice been a victim of copyright infringement. In examining his site, I noticed that he used the same arrangement, the same links, including access to some of our databases, and the same text. I was quite surprised to see significant sections of my content, including illustrations, integrated as part of his site with no mention of my work and in contravention of our agreement.