Recently I started receiving hundreds "Thank you for signing the guestbook" messages to my e-mail address. Apparently someone ran a script to find SPAM-prone GuestBooks to post their SPAM with my website e-mail address. As a result I'm getting a “thank you” note from every such post.
 

Now that's very annoying!

I took a quick look at web site log files and it seems most of spambots guest book signing requests were coming from these IP's bellow:

195.225.176.73

212.1.252.243

80.86.244.202

Dear spammers: I'm not sure what's the point of having your web site links in someone's guest books?? Having so does not improve your site ranking in Google index. It will not make anyone to visit that posted link either.

Doing so will only irritate web site owners and may be will force them to install some anti-spam feature for their guestbooks such as Captcha for instance.

Anyway for those who are running their mail servers using Postfix: Filtering these messages would not be a problem. Just adjust body_checks to filter out such “thank you notes” as described in Postfix documentation at http://www.postfix.org/

or more details available here

As for webmasters: Please do not use Guestbooks if they do not have some sort of anti-spamming feature, or at least please disable “thank you” auto-responders!