Email not working on 4.1

Hi
I have a problem sending email to clients via NOPCOMERCE 4.1. The system only sends mail to the site administrator and the client alert mail remains in the queue
The mail settings are correct but I do not know where the problem is from why the messages remain in the queue

Hello,

Did you check system log of your store?

hi
I chick the log

Log level  :Error
Short message  :Error sending e-mail. Mailbox unavailable. The server response was: <[email protected]> No such user here
Full message   System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: <[email protected]> No such user here
   at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception)
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at Nop.Services.Messages.EmailSender.SendEmail(EmailAccount emailAccount, String subject, String body, String fromAddress, String fromName, String toAddress, String toName, String replyTo, String replyToName, IEnumerable`1 bcc, IEnumerable`1 cc, String attachmentFilePath, String attachmentFileName, Int32 attachedDownloadId, IDictionary`2 headers) in E:\nopCommerce\sources\src\Libraries\Nop.Services\Messages\EmailSender.cs:line 153
   at Nop.Services.Messages.QueuedMessagesSendTask.Execute() in E:\nopCommerce\sources\src\Libraries\Nop.Services\Messages\QueuedMessagesSendTask.cs:line 69

hi

can any one advice me

thanks

See if this helps
https://www.nopcommerce.com/boards/t/57499/customer-order-emails-bug.aspx#217453