No, you can't change the aliases around. That will definitely break the list.
The list 'lives' at lists.domain.com, but we automatically forward email for email@example.com to firstname.lastname@example.org.
I actually thought about it more and I don't think my suggestion would work for you anyway, though. Sorry for the false hope!
Note that Mailman itself does have some built-in spam filtering you can use. Also, the very best way to keep spam off of your discussion list is to restrict list posting to list subscribers only. If you don't do that you will definitely get spam to the list.
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