If you can postpone it, it's best. I'm at home all day and have written a couple of times in the playgroup, but it's no problem if you can postpone it, it's better.
Still have to message your opponent after challenging. Messages get lost in there, private/direct messages are harder to miss. Also if you haven't heard from your opponent after 24 hours you're supposed to notify Knifemarre so he can message as well to make sure things aren't missed
D2:R