I have also been looking for the old functionality of the mailblocking contrib. Specifically, the ability to limit mail to only the domain you want the particular email address associated with. I realize that it can be accomplished with pseudonyms as mentioned earlier.
It appears that we get that same operation by just deleting the entries in /var/service/qpsmtpd/config/goodrcptto to leave just the entry you want to receive the mail. Of course, during any email-update event this file is overwritten. Maybe someone could add a template similar to the one in the mailblock contrib that rewrote this file with the addresses deselected that you didn't want.
It also seems that in setups with many virtual domains that these other email addresses are also vectors for spam that also have to be dealt with, instead of being rejected early on in the process. If we have fred@domain1.com that we want to get email, then fred@domain2.com, fred@domain3.com, etc. are all getting the same spam, if it makes it through.