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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How to Fix SMTP 550 5.7.1 Unable to Relay Error on Windows Server 2012 R2 | IT Nota
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Mailbox unavailable. The server response was: 5.7.1
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
Mailbox unavailable. The server response was: 5.7.1 Unable to relay for abc@gmail.com - Stack Overflow
c# - Mailbox unavailable. The server response was: 5.7.1 Unable to relay Error - Stack Overflow
5.7.1 Unable to relay to External Email address when sending email to Windows NLB ?
How to fix "554 5.7.1 : Relay access denied" email errors in web hosting servers
Inbound Email is Getting a Response of 530 5.7.1 Client was not authenticated.
SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Authenticat - C#
SMTP Exception: 550 5.7.1 Unable to Relay - CodeProject
The server response was 550 5.7.1 unable to relay for
550 5.7.54 SMTP; Unable to relay recipient in non-accepted domain - Microsoft Q&A
FIX: Relay Access Denied 554 5.7.1 Error in Outlook (Solved) - wintips.org - Windows Tips & How-tos
