Try a basic quad core, 8gb ram, 5k TB or more dedi and see how that works out for you cuz imo, servers specs are usually the least of my concern when sending to large lists. It's usually spent trying to get aol, yahoo and gmail to accept a lot of my mail plus warming up and keeping complaints/bounces low and engagement high. But i've sent millions to various hosts, and hundreds of thousands on the more popular ISPs like gmail using these specs. Depends a lot on your mta too if its optimized efficiently
Ah wow I see. Nice.I've sent millions to GI using the above specs. Today i was able to send about 600-700k on a 2 core vps on 1 IP for my campaigns being sent to various hosts (GI...)
I'm not using mailwizz for these campaigns though so i'm not sure how customized the MTA is. The tunneling also makes it less hardware intensive.
Not saying a powerful box won't help but i've been doing this for years and usually i just make sure its a quad core with at least 5tb bandwidth. I always get a bandwidth addon if the price is good cuz i think that matters more than the hardware at this point.