Please check that the email address you have entered is correct.
If the email is correct, it could be that our email was caught by recipient's spam filter. We do everything we can to by-pass spam filters but sometimes unfortunately it happens anyway.
Please ask the recipient to check their spam filter and mark our emails as "Not Spam" if they find them there. Another option to avoid our emails getting caught in a spam filter is to add our email address firstname.lastname@example.org to address book, this way signifying that we are a trusted sender.