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failure sending mail: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL
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Unable to send to all recipients … Mailbox unavailable. The server response was: 5.7.1 Unable to relay for … – Steve Ngai (危 志 荣)
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The only true wisdom is in knowing you know nothing.: Mailbox unavailable. The server response was: 5.7.1 Unable to relay sendername
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Mailbox unavailable. The server response was: 5.7.1 Unable to relay for abc@gmail.com - Stack Overflow
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SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Authenticat - C#
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