Poor deliverability rate | WordPress.org

this is a first run of an existing mailing list of 1000 recipients, delivered with another software since today.
delivery was blocked after 400 sent emails.
i should contact the support team to reenable the account.
where can i see the failed deliveries or what else caused the poor deliverability rate?
so i can delete the defect members from this mailing list.

The page I need help with: [log in to see the link]

 

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