Pending emails may result from improperly configured auto-responder plugins, such as 'Auto Response Plus.' When these plugins are activated but not fully set up, they can cause essential email fields—such as the recipient address and email body—to remain empty. Additionally, the email subject may not match the intended content, leading to errors flagged as 'Recipients' in the system. This misconfiguration prevents emails from being sent successfully and leaves them in a pending state. To resolve this issue, review the configuration of all active plugins and ensure each one is set up correctly to populate the necessary fields in outgoing emails.