How delivery rates are calculated – and why there’s no simple answer

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…

Deliverability rate given by your ESP = Non-bounce emails rate

Among all the contacts targeted, some of those will bounce because the email address does not exist anymore, or for temporary issues (full mailbox, server down, etc.). There are two kinds of bounces:

  • HardBounce: Means the recipient has an invalid email address. You highly recommend you to exclude this email address from next campaigns.
  • SoftBounce: The ISP confirms that the email address is valid, but cannot deliver your message to the recipient

Therefore, your ESP sends your campaign to your whole target group, and receives the answers from the ISP: Success, Hardbounce, Softbounce. Based on the number of Successes, you can calculate your Delivery rate seen by the platform. However, you don’t have any clue on what is done by the ISP once your email campaign succeeds…

Deliverability rate given by the ISP = Inbox rate

The ISP can deliver a successful email into the inbox, or the junk folder. His own rules are hidden to detect spammers, so you never know when you arrive into the inbox, or one of the other folders. :

gns, the ISP can send your email into his junk box, to protect his customer from annoying content.

If your content is detected as risky, it reaches the “no man’s land”, where no one can access to your email.

In all three scenarios, the ISP‘s answer to your campaign is “Success”

External companies like MailMike, 250ok or ReturnPath, can give you insights into which folder your campaign reaches. You can then approach your real inbox rate.

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