I noticed some newly registered users were not being authorised. Wondered why they did not click on the verified email.

I clicked on authorise from the admin panel and I get a big green tick for the user then being authorised but in the next breath DNN spits out the below error??

Error: is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: Mailbox unavailable. The server response was: 5.7.1 Unable to relay ---> System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.7.1 Unable to relay at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at DotNetNuke.Services.Mail.Mail.SendEmail(String fromAddress, String senderAddress, String toAddress, String subject, String body) at DotNetNuke.Services.Mail.Mail.SendMail(UserInfo user, MessageType msgType, PortalSettings settings) at DotNetNuke.Modules.Admin.Users.ManageUsers.MembershipAuthorized(Object sender, EventArgs e) --- End of inner exception

Any suggestions on how to rsolve this issue would be welcomed.

Thanks - DNNstar