You say 30,000 per day, but the interesting question is more how many per second or minute? And how good are your addresses?
30,000 spread evenly across a day is one email every 2.88 seconds, virtually nothing for any old system you can make into a server; even if you do it all single-threaded. Spread into two batches expected to be delivered in half an hour, you're talking about slightly over 8 emails per second; maybe a bit hard for that old 386 in the closet to manage, but doable with the right software on virtually any box bought in the last 5 years. Expect to deliver 99% of that 30,000 within a 1 minute window, and you're talking 500 per second; something a bit hard to do.
The most important spec will be memory. Email deliveries take no real computational effort, the main thing is that you'll want to have a lot of open outgoing connections to different servers, and the way to do that is multiple processes or threads, which means more RAM.
If an address gives you a temporary error, do you want to save it out to a queue and try it again later? Some people are set up so that that's the only way to get email to them.
Really, for those volumes, the hard part is dealing with bounces, unsubscribes and spam complaints. (and if you don't handle those properly, you'll be flagged as a spammer in the various databases and won't get your email through)
For that matter, is your business plan to spam? Where did those 30,000 email addresses come from?