Many people have difficulties in receiving an e-mail? What the hell are you talking about? There is no difficulty in receiving an e-mail and most importantly an e-mail is received by the mail server, not by the people, so the people cannot possibly have any difficulty whatsoever. This flagrant lie is your reason why you are trying to sell free accounts for $20? Shame on you.
No related to this at all but there s a misunderstanding, Microworkers send the PIN in mail "yes, mail as in regular mail". Of course there are difficulties in receiving it in parts of the world.
OP what country does that account belong to? if it's US it may worth something...