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I've added the Send As permission in Exchange Management Console | Recipient Configuration | Mailbox | right click on the mailbox -&gt; Manage Send As Permission.<br />
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I've created a profile in Database Mail in SQL server to use this mailbox and added the SQL Server's IP in Exchange Management Console to Sever Configuration | Hub Transport | Receive Connectors | Default &lt;servername&gt; | Network tab | Receive mail from remote servers that have these IP addresses<br />
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I am getting the following message:<br />
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The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Client was not authenticated).<br />
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How can I fix this?<br />

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Check this link, it might help:<br />
<a href="https://www.experts-exchange.com/questions/23063340/Sending-email.html" rel="ugc">https://www.experts-exchange.com/questions/23063340/Sending-email.html</a>
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The answers helped, but I had to do one more step:<br />
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In Server Configuration | Hub Transport | Receive Connectors -&gt; Default &lt;server name&gt;, I've set in:<br />
Authentication: TLS and Externally Secured + unchecked everything else<br />
Permission Group: Exchange Servers + unchecked everything else<br />

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We use email client code in one of our applications.<br />
When I try to configure it to send email through an account called smtp_mail&nbsp;from Exchange 2007, the log file shows the following error:<br />
<br />
Exception occured while trying to send the email with the subject MBS Selection <br />
System.Net.Mail.SmtpExcept<wbr />ion: Mailbox unavailable. The server response was: 5.7.1 Client does not have permissions to send as this sender<br />
<br />
Somebody suggested the following command:<br />
get-receiveconnector &quot;Client exch-mbs&quot; | add-adpermission smtp_mail AU -extendedrights ms-Exch-SMTP-Accept-Author<wbr />itative-Do<wbr />main-Sende<wbr />r<br />
<br />
But when I launch it, it says:<br />
<br />
Add-ADPermission : A parameter cannot be found that matches parameter name 'AU'.<br />
At line:1 char:58<br />
+ get-receiveconnector &quot;Client exch-mbs&quot; | add-adpermission &nbsp;&lt;&lt;&lt;&lt; smtp_mail AU -extendedrights ms-Exch-SMTP-Accept-Author<wbr />itative-Do<wbr />main-Sende<wbr />r
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We use email client code in one of our applications.
When I try to configure it to send email through an account called smtp_mail from Exchange 2007, the log file shows the following error:

Exception occured while trying to send the email with the subject MBS Selection 
System.Net.Mail.SmtpException: Mailbox unavailable. The server response was: 5.7.1 Client does not have permissions to send as this sender

Somebody suggested the following command:
get-receiveconnector "Client exch-mbs" | add-adpermission smtp_mail AU -extendedrights ms-Exch-SMTP-Accept-Authoritative-Domain-Sender

But when I launch it, it says:

Add-ADPermission : A parameter cannot be found that matches parameter name 'AU'.
At line:1 char:58
+ get-receiveconnector "Client exch-mbs" | add-adpermission  <<<< smtp_mail AU -extendedrights ms-Exch-SMTP-Accept-Authoritative-Domain-Sender

Permission issues when sending SMTP mail

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