This is the first time I’ve encountered this:

Today I replied to a thank you e-mail sent by someone who appreciated the information available at search-explore.com. When I tried to reply, I received this message:

Hello, you recently sent a message to me at *****@hotmail.com.
I am now using a mailbox protection system called ChoiceMail One to block unsolicted junk mail. Because you are actually reading this note, it is highly unlikely that your message to me was in fact unsolicited. However, I regret that I do not already have your email address in my whitelist. That is why this note has been sent to you.

Please click on the link below to verify your identity.

When your browser opens, fill in your name and a short reason for wishing to send e-mail to me. Your message will be delivered to me after I review this information.

There is no need to send your original message again.

The information you provide will only be seen by me and is not saved by DigiPortal Software for any purpose.

To find out how ChoiceMail One can help prevent your own inbox from overflowing with junk e-mail, you can visit DigiPortal Software’s web site.

More details about the registration process itself can be found here.

Please be aware that a response is required within 4 day(s) to prevent your messages from being automatically deleted.

When I clicked the link, I was asked to answer two questions: what is my name, and why do I want to e-mail this person. Then I was asked to type the numbers that appeared in a graphic area above the entry field. Shortly after, I received notification that my message had gone through the the recipiant and that I was now on her “whitelist.”

A clumsy, but seemingly effective, way to block spam.