The delivery rate together with the bounce rate results in the quantity sent. However, it does not mean that your newsletter has reached the recipient's inbox. It is only the resultant of the delivery rate minus bounces, i.e. rejected e-mails. For example, an email can still end up in the recipient's spam folder and thus not actually reach him or her. Here again, reputation has an effect. E-mails with a bad reputation are often filtered out by e-mail providers.
Compliance with e-mail hygiene rules is therefore a fundamental prerequisite for a high delivery rate.