Delivery rate or inbox placement rate is the folder placement performance metrics of sent mail after being accepted or delivered.
To calculate the deliverability rate (in percentage), divide the number of emails delivered by the number of emails sent and multiply by 100. The email service provider may provide you with your deliverability rate, either in your campaign analytics section or on your dashboard.
Do not confuse the deliverability rate with your delivery rate or bounce rate. The latter is a measure of emails that are not delivered and subsequently returned to you. Emails getting bounced may be due to factors like incorrect email address, lack of permission – either the recipient has blocked you or has not opted-in to receive your emails and a full inbox.
Emails not getting delivered is a result of the email server (Gmail’s Google or Microsoft’s Outlook) blocking them or the server experiencing issues or not existing in the first place. In the case of temporary failures, the email server retries delivery within the following 72 hours before marking it undeliverable. The time is to allow the server to resolve any issue it may be facing.