Run a honeypot. Just an usual Postfix with catch-all virtual mailbox and a learn-spam for the destinatin. Let spammers happily fill it (they will, in no time) and train your very own rspamd/spamassasin/whatever.
Sure, this works as long as they don't try to poison your filters, but given its a small and rare target, it's unlikely someone would bother.
A proper honeypot takes a lot of time and effort. You actually have to inject that email into the right environments. For example nobody will steal your honeypot address from someone's mail history, some service's stolen user database, or others.
Sure, this works as long as they don't try to poison your filters, but given its a small and rare target, it's unlikely someone would bother.