Deliverability is affected by the IP address's trustworthiness and a few other factors. Avoiding spam filer is a bit harder as you likely have to set up your promotions to be way different from what most people think is normal. Add easy unsub headers, send few emails, make sure you don't send regular emails that have very low open rates, etc. You might be marked as spam (personally I don't mark as spam unless the unsubscribe request is ignored, or unwanted emails are sent daily).
For example, I always open Microcenter's somewhat frequent emails, so I'm probably beneficial to them. Make frequent newsletters or marketing opt-in, this will not only keep open rates high (only interested readers will sign up, thus high open rates) but will also help avoid more ML-based spam filters that take open rates into consideration. You might be classed under "promotions" in Gmail regardless but that's less bad than classed as spam.
