I've recently been plagued by floods of spam from the unscrupulous "Sleuth" group of marketing companies (probably because my partner once clicked "unsubscribe" on one, which predictably had the opposite effect.) I believe the company is legitimate, technically speaking, and the emails pass all the usual admin-level spam filters (SPF, DKIM etc.), so I've had to add a custom spam filter on the user inbox for "Sleuth" in the subject. This works Ok, but I'd prefer to simply blacklist these at the admin level so they're bounced and I don't receive them at all.

The problem is that the sender address (no doubt quite deliberately) is from a range of domains, and even worse they're prefixed by a randomly varying letter, e.g. e.crowdingproperty.co.uk, i.crowdingproperty.co.uk, n.crowdingproperty.co.uk etc. Of course I can add these individually to the blacklist, but attempting to add a wildcarded domain such as *.crowdingproperty.co.uk is rejected with an "Invalid domain" error (see attached). It would be really useful if the blacklist (and other) domains allowed wildcards, in the same way that PC utilities such as CCleaner allow wildcarded cookie exceptions such as *.amazon.co.uk or *.google.co.uk.

Thanks.