To find out the status of each subscriber on a mailing list, you can download the mailing list in the ESP dashboard as a CSV file under Emails → Mailing lists → clicking on the ellipsis (three dots) menu on the right-hand side next to the respective mailing list ID → Download mailing list.
Once the download is complete (it might take a minute or two for larger mailing lists), in the CSV file you will see a column B with the Status of the subscriber.
0 - the user is not subscribed, because they were deactivated via API, dashboard, or email
2 - the user is pending email verification. When Double-Opt-In (DOI) is enabled, new users receive a verification email and will remain in this status until they verify their email address via the verification link.
-2 - the user is not subscribed, because they have received a hard bounce (invalid email)
-3 - the user is not subscribed, because they have marked the email as spam
-5 - the user is unengaged. An unengaged user is defined as an active user who has not opened or clicked any emails from any campaign of the publisher within a defined check period. More details can be found here.
-9 - the user is not subscribed, because their email address was blacklisted by ESP*
And 1 means that the user is currently subscribed.
We consider -2, -3, and -9 statuses as hard bounces and don't send them any further newsletters.
Users with status 1 can potentially have a soft bounce, but we continue sending them emails until either a hard bounce occurs or our heuristical algorithm determines, that they should be deactivated due to the non-deliverability of emails.
If you see any deferrals in the Deliverability graph report, this usually means that there is an issue on the receiving email server, that temporarily limits the email sending. We will attempt to deliver the email until it either will be delivered successfully or we receive a bounce error.
We don't have any report available via the Piano ESP dashboard's UI that would list users with soft bounces or deferrals.
*We are trying to protect the e-mail reputation of our clients because repetitive e-mail sendings from untrusted or spam sources tend to decrease the sender's reputation, which as a result leads to an increased percentage ratio of e-mails getting into spam traps and not being delivered to end users.
In order to avoid that, our system validates any incoming e-mail and if it should be blacklisted, it will be done upon the attempt of subscribing such a user. There can be many reasons why ESP blacklisted an e-mail, one of which is when the e-mail is related to automated disposable e-mail systems, such as Mailinator, or spam traps. With such systems or services, anyone can spoof e-mail traffic and decrease the sender's reputation, and such e-mail addresses can not represent a valid recipient.