> I'm sorry to hear that you are erroneously receiving email from 
> Astrology.com. Most likely, one of our customers has entered your email 
> address in  error, 

No, someone  abused misconfigured  systems like yours  and subscribed  me to
more than 100 mailing lists.

> and unfortunately we do not have a way to prevent this from happening. We 
> appreciate your feedback  and we will promptly remove  your email address 
> from our mailing list.                                                    

Yes, you  do have  a way to  prevent this from  happening, you  should never
trust any input from the web, and you should certainly not subscribe someone
to your  mailing list until you've  verified that this person  is really the
one who entered the Email on you web site.
That's called a 3 way handshake.

Scenario #1:
You Email me with a URL that has a unique number appended to it.
If I click on it, your server gets confirmation that it was me who asked to
subscribe, and subscribes me for good
(if I don't, you drop the request)

Scenario #2:
You Email me with a password/unique ID/whatever, and when I answer the mail,
your system confirms my subscription just like above.