Online communities, such as social networks or forums usually employ system emails to inform their users about community-internal processes. The community provider must guarantee that the sent system emails will reach the recipient. In order to track the delivery of system emails, there are three important performance figures.
When a user receives a message from another user within a community platform, e.g. via an internal messenger or because one of his posts are commented on, this leads to the automatic sending of a system email in most communities – as long as the user has opted for it. This system email informs the use about the new message. System emails usually do not contain any commercial content of the community provider, but are primarily a service for users. It is therefore very much in the interest of the provider to guarantee the delivery of emails. In order to track this, there are three relevant performance figures. As system emails are sent individually to each user, the performance figures cannot be determined for fixed limited sendings, e.g. a newsletter edition. Instead, all system emails of a specific period are included.

Delivery Rate

The number of sent emails is the dispatch quantity. Sending an email does not necessarily mean that this email will reach the recipient, i.e. it is delivered. An email, which has been sent but not delivered, is called a bounce. We distinguish between soft bounces and hard bounces. Soft bounces are emails, which temporarily cannot be delivered due to temporary events, e.g. a full inbox. Hard bounces are emails, which permanently cannot be delivered. A reason could be that a targeted inbox does not exist anymore. By subtracting the bounces from the dispatch quantity, we receive the delivered amount. The delivery rate results from the ratio between delivery quantity and dispatch quantity. It shows the percentage of sent emails, which have been delivered.
Delivery Rate = (Dispatch Rate – Bounces) / Dispatch Quantity * 100

Bounce Rate

The opposite of delivery rate is the bounce rate. This shows the percental relation between dispatch quantity and bounces. The bounce rate can also be established from the difference of 100% and the delivery rate. If a delivery rate is unsatisfactory, it is useful to look at the respective percentage of hard bounces (hard bounce rate) and soft bounces (soft bounce rate) of the total dispatch quantity for a more in depth analysis.
Bounce Rate = Bounces / Dispatch Quantity * 100
Hard Bounce Rate = Hard Bounces / Dispatch Quantity * 100
Soft Bounce Rate = Soft Bounces / Dispatch Quantity * 100

Inbox Placement Rate

The inbox placement rate is similar to the delivery rate, but here, only emails are counted, which have actually been displayed in the recipient’s inbox. The delivery rate is cleared from emails, which end up in the recipient’s spam folder. This cleared amount is then set in a ratio to the dispatch quantity.
Inbox Placement Rate = Number of emails actually displayed in the inbox / dispatch quantity * 100