We could talk about Deliverability as everyone, we choose to talk about it as no one.
Today, more than 60% of the whole email traffic is spam (statistica, 2016). This means ISPs have more chance to receive a spam attack, or a risk to his customer, than an important emailing.
Your ISP can proudly show it has a 99% Deliverability rate, nevertheless evidently you receive your emails in the junk folder, or you are blocked to a specific ISP. How can this be? Why is my Deliverability so high on some ISPs and not on all ISPs? Why do I have 99% Deliverability rate but the ISPs still consider me as a spammer? The indicators are just not calculated the same way…