Hello @Karin,
Thank you for sharing that information with the Klaviyo Community. I understand this can be frustrating, but I am happy to provide some assistance.
Suspicious emails are email addresses that have hard bounced at least once across the Klaviyo infrastructure even if they have never hard bounced in your account. While you cannot unblock a suspicious email yourself, our support team can unblock a suspicious email address for you. The quickest way to get this resolved would be reaching out to support with the subject “Remove Suspicious Email” and provide screenshots of a recent email correspondence (thread) with the email address in question within your request. Once the team has screenshots of this email address sending/receiving email, they can remove the suspicious status which will allow the email address to receive email again.
Thanks and have a wonderful day.