Board Thread:General Discussion/@comment-13918697-20130930214758/@comment-11733175-20131001000212

As mentioned by Joshua above, you can email people using Special:EmailUser if they have enabled it in their preferences (as you've seen). To email me for instance, go to Special:EmailUser/Cqm. For someone else, replace Cqm with the user you want to email.

Bear in mind if you do email someone, you will reveal your own email address and if they reply they will reveal theirs. If you don't want to reveal your normal email address you can alter your email to a throwaway account on somewhere like gmail. You can set up forwarding from that throwaway account so you don't miss emails too.