how-to-dormspam@ does not manage dormspam, and cannot subscribe or unsubscribe you. You have to remove yourself. See below for how to do so.
Dormspam gets sent to several different mailing lists, each of which receives some traffic that is not just dormpub.
To subscribe to dormspam, simply add yourself to one of the lists (you should probably do the one you’re most associated with, as they also are used for non-dormspam content; if you aren’t affiliated with any and want to be on dormspam, I recommend bc-talk, which has relatively few emails intended for only BC residents). These lists are opt-in, and first-years are not added by default. However, how-to-dormspam (and many upperclassmen) strongly encourage you to add yourself to receive information about clubs and events on campus!
To unsubscribe from dormspam, remove yourself from all lists that you’re on. Note that removing yourself from these lists will cause you to miss other social emails that happen on these lists.