UseBestMail provides a mechanism for validating mail from non-UseBestMail correspondents. The basic element of this system is the "whitelist". A whitelist, the opposite of a blacklist, permits your system to receive mail from anyone on the list, even if the mail is not stamped.
Addresses are automatically added to the UseBestMail whitelist whenever you send an email, the philosophy being that you are willing to receive mail from anyone you send mail to. The system also enables you to manually add email addresses to the whitelist and to remove addresses you don't want there.
Another way of adding an address to the whitelist is to send a special email to the sender of an email from someone who isn't on your whitelist and doesn't UseBestMail. This message is automatically generated for you while the sender's email is held on the server. The figure below shows the content of the email the sender receives.
The automated message is called a challenge message. It explains that since you don't know who the sender is you'd like to verify that it isn't from an automated source, but rather from a human. The sender is asked to click a link ("Click here to validate the email," above) and take a little test by typing in some numbers that are shown in graphic format that a machine can't understand. This is shown below.
If the user responds to this challenge he is informed that his email will now be delivered to you without further ado as shown below:
The UseBestMail web server that administered the challenge, above, now generates an email message that is sent to your address. The message has a UseBestMail stamp. Your UseBestMail software interprets this message as special due to its unique stamp. The sender's address is added to your whitelist and his email is promptly delivered to your inbox. The automated message is deleted since it has now done its work.
