Gmail is the best email service and the mails in the deferred queue are retired constantly unless time out is reached. The action “queued for delivery” means that the mail is already is HES outbound MTA but for some reason, has not been accepted by the receiving mail server because of a temporary error. Also, check the network connection as sometimes a weak signal might create an issue while sending emails. Check that you are using the updated Gmail version and you are using a strong and stable network connection and call on Gmail support number UK to get connected with the experts.