Can I send messages to someone that I have blocked?

No. Blocking someone from your Friends list prevents you from contacting that person also. If you need to get in touch, you can unblock the person by following these steps:
  1. Click 'Settings' at the top of your Friends list.
  2. Highlight 'Blocked' along the left side of the dialogue box and select the name of the user that you would like to unblock.
  3. Click 'Unblock' on the right side and then click 'OK'.
Keep in mind that if the person whom you unblock has blocked you also, you will not be able to talk until he or she has unblocked you, too.