If this guy clearly believes he may still have a chance you need to reiterate that you are not interested, apologize for your behaviour and then stop emailing him before you really hurt him or it gets too serious.
If you are emailing somebody a formal email than yes. If you are just emailing a friend you don't necessarily have to but I do just because my mom always did. I learned from her. My friend though when emailing me does not and its OK
Lotus is a site that has an emailing feature. If you don't know the answer to this, then maybe I have the wring one, because it's pretty obvious. Lotus emailing is like Gmail or Hotmail or Yahoo. It is just another site to check your email on. If you need a bigger answer, then specify that.