@yarmo For outbound, it's the deliverability. Even major players can just vanish off the face of big name destinations like Microsoft; who accept SMTP but then decide to not give it to inbox (or even to spam).
But there's also the inbound - when 90% of the connections being made to you are for spam, what technique do you use to block them?
Paying for a reputation blacklist of IPs would be nice, but you only get that in an actual vendor product.
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