1. A method for transmitting an email message to multiple groups of recipients, the method comprising: composing an email message including digitally encoded content, email addresses associated with a first group of intended recipients, and email addresses associated with a second group of intended recipients; entering the email addresses associated with the first group of intended recipients into a first “to:” field; entering the email addresses associated with the second group of intended recipients into a second “to:” field; sending the email message to the first and second groups of intended recipients; preventing the first group of intended recipients from determining the identities of the second group of intended recipients, and preventing the second group of intended recipients from determining the identities of the first group of intended recipients; and enabling the intended recipients of the first group to know the identities of intended recipients within the first group, and enabling the intended recipients of the second group to know the identities of intended recipients within the second group.