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shared mailbox with sendas issue

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I created two shared mailboxes and Distribution Groups/security groups with them.  Everything works fine except when sendas to extrenal people.  I get this resolute.

 

Your message couldn't be delivered because you weren't recognized as a valid sender. Make sure your sending address is set up correctly and try to send the message again. If the problem continues, please contact your helpdesk.

The following organization rejected your message: CO9EHSMHS028.bigfish.com.

 

Everyone can see the boxes.  They receive emails and send emails to internal people fine.  The only issue is when you send to outside address.

 

Error message one more time.

 

Your message couldn't be delivered because you weren't recognized as a valid sender. Make sure your sending address is set up correctly and try to send the message again. If the problem continues, please contact your helpdesk.
 
The following organization rejected your message: CO9EHSMHS028.bigfish.com.

 

 

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  • Hi Jon,

    This issue may be caused by the reason that the Office 365 email address has been added into their blacklist.

    To troubleshoot this issue, you can contact the recipients to check if they have blocked your Office 365 email addresses in their email. Meanwhile, please test if you can send emails successfully to a Hotmail account.

    If the issue persists, please send the detailed non-delivery report (NDR) to me. I have sent a private message with a subject of < shared mailbox with SendAs issue) > to you.

    To access the private message:

    -Go to your details section on the right side of the community site.

    -Click Private messages.

    -Click the subject title of the response to read the message

    Thanks,

    Jerry Cen

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  • Hi Jon,

    How are things going ? If you need further assistance on this issue, please feel free to contact us.

    Best regards,

    Jerry Cen

    • Top 50 Contributor
    • Post Points: 0
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