External mail clients (Postbox 3.0.9) can not send email 550 5.7.1 Client does not have permissions to send as this sender

Hi There,

Exchange 2010 environment.

External users can't not send email using Postbox (mac client)

Internal users are not affected just external users.
This was working perfectly fine in the past.

The error is: 550 5.7.1 Client does not have permissions to send as this sender

The same external users can send emails using Smartphone (Iphones) but not via email client.

Thanks, Rod
Rodrigo CarrilhoAsked:
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Rodrigo CarrilhoConnect With a Mentor Author Commented:
thank you for the comments.

I managed to solve the problem by giving full permission the mailbox user itself.
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Andy MInternal Systems ManagerCommented:
Hello

What connection method is the Postbox software using to connect to the Exchange server? POP/SMTP, IMAP, EWS, OWA?

iPhones and Email clients connect in different ways to the exchange server. The phones use Activesync where as the email clients use one of the above connection methods. The fact that the phone works indicates the account is working with regars to sending/recieving email so the issue will be with the connection methdo used by the Mac client.
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Jamie McKillopIT ManagerCommented:
Hello,

Make sure the client is set to authenticate before sending.

-JJ
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Rodrigo CarrilhoAuthor Commented:
I managed to solve the problem by giving full permission the mailbox user itself.
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