Ask HN: What is the best way to setup a 2sd transactional email server?

Hello HN Crowd,

5 years ago, I've setup a transactional email server for a non-profit. It took me a while to figure things out (properly setup DKIM, SPF, throttle emails for some providers, etc.), but now it can send up to 1 million emails per month (up to 70,000 per day) without those emails being blocked or sent in SPAM.

I can't take all the merit here. This is a non-profit and people really do want to receive those emails.

Anyhow, the non-profit now wants a 2sd email server and here's my question: how to I set up this? After the usual setup, do I just start sending half of our emails through the new server and ip? Or should I send only 10 % and ramp it up to 50 % progressively?

Any advice is welcome! Thank you very much!