I think that some good advice has come about on this thread...but I have one VERY friendly word of caution.
I feel that using "Attempt #1" could be contextually aggressive. I KNOW how ancy one can get waiting for a return e-mail or call; please consider that, in some areas, numbering one's e-mails could be seen as aggressive. However, I am not sure of a better way to elicit response.....
Just a humble and, again, friendly thought...
Silver