It is a sad thing how some people use their effort and creative capacity to produce spambots...

Deleting the failure notices isn't a problem, and so far I've thought that it is a minor nuisance especially if I don't ever click on any link in these messages. But yesterday I noticed that towards the end of the day I started getting messages from my webhosting service - error messages saying that an outgoing message was blocked because daily error limit was exceeded. Either that is yet another version of spam mail trying to make me click on a malicious link, or then my webhotel really has a security bot blocking mail accounts which seem to be hijacked or something...

So now I'm experimenting with CAPTCHA to see if I can stop spam subscriptions.