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I am using roundcube for web client, when I compose an email address with one of the TO/CC/BCC address mispelled and click send, the web client keeps rotating and finally comes back to the compose, and the email is not sent to any recipient, looking on the error log i find something like SMTP Error: SMTP error: Failed to add recipient xxx@yyy.com while that recipient is an external domain. What wrong with my settings? I would expected that the email is sent and should get a bounce back email of not delivered email but its not the case.