I get a hell of a lot of spammy accounts register to my forum every month. This isn't a problem because all members' first post must be approved and we mark them as spammers/banned.

However, the downside is that these spam accounts clutter the member list, which causes problems when exporting emails for our newsletter.

Is there a quick way to remove these accounts without having to go through them one by one?

Are you flagging the users as spam using our tool? If so, this should likely remove them from being eligible for admin emails, unless you're exporting emails a different way.

Regardless, to mass prune those flagged spammers, you can use the following: https://invisioncommunity.com/forums/topic/484898-multi-selection-of-members-in-the-acp/#findComment-3010129