> why is email deliverability still an issue? Mostly what I've found as the main issue here is that popular blacklists will blacklist entire IP blocks instead

> why is email deliverability still an issue? Mostly what I've found as the main issue here is that popular blacklists will blacklist entire IP blocks instead of individual IPs, so you have to not only have a clean IP but also be on at least a /24 with all clean IPs. This can be hard to manage when relying on outside hosting. And unfortunately, trying to get around it by using a cheap/free relay like Amazon SES or SendGrid doesn't work, as they fail to keep their IPs clean (if they're even trying).