Handshake or blank message spam

I’ve been getting a lot of blank message spam. Seems to me some spammer is just handshaking the server to find addresses to send to. Spamseive is not catching these since the sender address is constantly changing.
Is there something I can do? I’ve reset the corpus and re trained, but no matter homw many times I train message as spam, it keeps coming into my inbox.

Second option: Is there a rule I can set up in mail.app to direct blank messages to the spam box.

If a particular kind of spam message keeps getting through, please report it. First, this will help you verify that the message is actually getting through SpamSieve (and not ending up in your inbox for some other reason). Second, it will help me improve SpamSieve to deal with this kind of message.

I do not recommend creating rules in Mail to deal with particular kinds of spam. Instead, use SpamSieve’s blocklist. If the messages truly are blank, then you should be able to catch them with a blocklist rule that says:

Body (Any Text Part) Is Equal to

where the “Text to Match” column is left blank.