Very few ISPs conform to the old spam score placement.  Where an email content and subject line were examined and based upon general rules were determined to look like junk or not.  Much more so now it is based on actual engagement with your message.  I would also point of that deliverability and inbox placement are not the same.  Deliverability is where your email is delivered to the ISP (such as Hotmail, Yahoo, Gmail etc.), this is the often-quoted delivery figure from your email provided, however how that ISP deals with your email can be very different.

Main elements effecting basic delivery of an email:

Domain Reputation

IP Reputation

Main elements effecting inbox placement:

Positives

Open/Read:

If a user frequently opens your email, this is a very big positive to keeping your email in the inbox.

Reply:

Responding to your email (using the reply address), again shows excellent metrics.  This can be a quick win.  Using a support@ or hello@ and responding to emails, rather than using a standard noreply@   Just a note: please be wary of how your email provider deals with out of office replies, or your inbox may fill up quickly 🙂

Out of Junk:

If a user locates your message, and moves it from junk to inbox.

Move to Another Folder:

Interaction with your email, and moving to specific named folders, shows the ISP that the user has made choices about how to deal with your email.

Add to Address Book:

If a user is added to their address book, then this again shows the user has some relationship with your company/brand etc.

Negatives

Complaints:

Marking your message as spam directly, which passes to your email provider as a complaint.  Is closely monitored.  Individually it will stop your user receiving the email, and over certain thresholds will start to block your email being delivered into the ISP directly.

Moving to Junk:

A user choosing to classify your message as junk, has a very strong influence on future messages.

Delete without Open:

Although not as strong as classifying as junk, this does imply a negative factor.

None of the positives:

Although this probably doesn't imply negatively, it is at best neutral, and at worst showing a pattern of behaviour.

It would be fair to say that based upon the engaged with the email, these factors not only effect inbox placement of current and future campaigns, but also will start to influence the delivery via domain and IP reputation.   Individually a user with the above metrics, can cause your email to appear in their inbox or not.  Whilst at the same time the total volume of all your emails, using the above metrics will impact on the overall domain/IP reputation.

This article is far too short to cover all elements, and we have listed here the main elements of engagement assuming a reasonable starting point.   If you have issues with delivery of your email.   Then hopefully there will be another article at 247EmailData to help you through those issues.  Including spam traps, complaints, blacklists, authentication etc.