We are having a big spam problem and we don't know how to resolve it. We have one spammer that send us mail daily. All these emails are from different themes, using different email addresses that are only used one time, and the domains are used only one time. So we don't have any way to stop it. The only pattern is that the domain names are really young and are registered the same day the spam is send. They use .us and .me domains.
Any suggestion to resolve this problem?
There's a project called the Anti Spam SMTP Proxy on SourceForge,
here: http://sourceforge.net/projects/assp/
You could build a server and put ASSP on it (Windows will probably be easiest)
and after a week or two of collecting spam and ham (non-spam) messages, you can begin to block spam.
A smart thing to do during the collection period is to send all of your past emails to a ham-collection address, which will whitelist and analyze the emails for words and recipients which should be trusted.
ASSP uses various techniques to score emails, so it can intelligently block the emails that you described in your post.
