What is the SendForensics Deliverability Score?

The SendForensics Deliverability Score is a measure of an email's 'quality' in terms of how it will be perceived by global filtering-systems and ISPs i.e. the likelihood of it passing into any given user's inbox.

However, given the relationship between deliverability and user-engagement, it is in fact a measure of an email's potential for engagement itself.

Ultimately, a higher SendForensics Deliverability Score = More clicks, less complaints

How is it calculated?

The score itself can be said to represent the percentage of inboxes in an average mailing list that an email will reach. It is calculated by modelling the email's acceptance against the behavioural spread of the worlds spam-filtering-systems/ISPs at time of analysis.

There are three assumptions that have to be made to correctly relate the score to an email/campaign:

  1. Mailing list is clean and fully-verified i.e. no bounces

  2. Mailing list is a globally ‘average list’ in terms of its list-composition. This is a list that reflects the broad distribution of receiving filtering-systems/ISPs worldwide.

  3. Mailing list is a globally ‘average list’ in terms of its prior engagement history i.e. from addresses that have never been sent to before from that domain/IP, to those having a long history of engagement with that sender.

The score is representative if these 'lab' conditions are met, but of course in practice each of these conditions will vary by differing amounts. Crucially, however, following the system's advice for fixing issues and improving the score will improve results under any conditions.


Engagement Results

It's impossible to know the exact number of emails in a campaign that reach their destination inboxes. The only truly reliable email metric following number of emails delivered is the number of resulting unique clicks. This is therefore the benchmark against which the SendForensics Deliverability Score is measured for its efficacy.

We regularly measure Deliverability Scores against resultant unique clicks across our user-base. For example, the scatter-graph shown is an analysis of engagement data performed on 03-Aug-2018 with 3,698 campaigns totalling over 145 million emails. There is a clear positive corellation in rising Deliverability Scores vs resultant click rate as can be seen from the trend-line.

It is important to appreciate that this is an average. All engagement data is noisy since a campaign with a high SendForensics Deliverability Score may suffer other problems (regarding the assumptions above), or simply be uninteresting to its recipients. However, as mentioned above, any boost to the Deliverability Score will, on average, improve deliverability and engagement for the campaign (by how much depends on the other factors).

Less Complaints

Whereas CTR/Unique-Clicks may be the most reliable performance indicator in email marketing, there is another important metric that benefits from higher quality emails: Spam Complaints. Too many complaints can taint your mailing reputation and affect the success of future campaigns.

The following is real customer campaign results over a one-month period, pulled directly from the Email Deliverability Suite (with ESP plugin enabled). In order to minimise fluctuations in other metrics and isolate the effect of the Deliverability Score on engagement, the newsletter was chosen for the following reasons:

  • Consistent offering (weekly listing of items for sale)
  • Consistent mailing-list size (55,400 contacts +- 250)

As can be seen, the deliverability score has a direct effect on the number of unique clicks. However, adding spam-complaint/abuse data to the same campaign dataset produces a startling pattern when the y2-axis is plotted logarithmically (for data-range comparison).

Deliverability Score vs Complaints

As can be seen, there is an almost perfect inverse-correlation between the Deliverability Score and number of spam-complaints registered.


  • The SendForensics Deliverability score is modelled in realtime on the behaviour of a comprehensive distribution of global receiving systems

  • Specific optimisations and advice impact individual systems by variable amounts, but affect them nevertheless

  • Ultimately, a higher SendForensics Deliverability Score = more clicks, less complaints

There are many variables that affect campaign success, with some rather more difficult to control than others. Now that it's possible to keep deliverability regularly in the sweet-spot, and pre-emptively before a campaign is sent, that's one less problem to worry about.