I run a few moderately sized corporate e-mail systems. SPF, DKIM, DMARC are all necessities, but unfortunately they don't guarantee delivery. We have much better success sending e-mail out via Mailgun or Sendgrid. Since Verizon swallowed up Yahoo Mail and @aol.com, it's very easy to get on their shadow ban list, and nearly impossible to get off. Good luck telling all the employees they can't email @yahoo.com and @aol.com for at least 2 weeks.
I see e-mail as another Internet service that is slowly centralizing, and if you operate outside of the big tech companies- for example, if you don't use Google/Yahoo/M365 e-mail, you're probably going to be in for a headache, even if you run perfect e-mail infrastructure.
I see e-mail as another Internet service that is slowly centralizing, and if you operate outside of the big tech companies- for example, if you don't use Google/Yahoo/M365 e-mail, you're probably going to be in for a headache, even if you run perfect e-mail infrastructure.