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Can you show us the headers (detailed headers) of a rejected message, including the error message?
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Can you show us the headers (detailed headers) of a rejected message, including the error message?

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Hello<br />
<br />
The only error we receive is in the ERP solution itself and states that the mailbox is unavailable and the server is not responding.
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Hello

The only error we receive is in the ERP solution itself and states that the mailbox is unavailable and the server is not responding.

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Hello<br />
We are using the O365 mail relay connectors to send email from a third party software. All emails sent to O365 hosted email domains are sent and received ok. If we try to send to an non hosted O365 email domain it gets rejected. How can we setup the smtp reply to send externally from o365 <br />
I thought setting up smtp authentication may do the trick but I can't find where to set this up on the O365 admin console.
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Hello
We are using the O365 mail relay connectors to send email from a third party software. All emails sent to O365 hosted email domains are sent and received ok. If we try to send to an non hosted O365 email domain it gets rejected. How can we setup the smtp reply to send externally from o365 
I thought setting up smtp authentication may do the trick but I can't find where to set this up on the O365 admin console.

Office 365 Mail SMTP Relay Issue

Office 365 is a group of software plus services subscriptions that provides productivity software and related services to its subscribers. Office 365 allows the use of Microsoft Office apps on Windows and OS X, provides storage space on Microsoft's cloud storage service OneDrive, and grants 60 Skype minutes per month. Office 365 includes e-mail and social networking services through hosted versions of Exchange Server, Skype for Business Server, SharePoint and Office Online, integration with Yammer, as well as access to the Office software. All of Office 365's components can be managed and configured through an online portal; users can be added manually, imported from a CSV file, or Office 365 can be set up for single sign-on with a local Active Directory using Active Directory Federation Services.