Thoughts on an absurd quantity of email boxes?

My boss wants me to create 90 email boxes for one of our clients (30 per rep) and I think that isn’t the best strategy. We are targeting large companies and her mindset is very spray and pray. I feel like it would be better to focus more on quality and niche targeting instead.

Any thoughts on this? What strategies do you use when targeting prospects at Fortune 500 level companies?