When external users try to send email messages to mail-enabled public folders in Office 365, they receive a nondelivery report (NDR) that contains the following error code:
Remote Server returned '<xxxxxxxx> #5.7.1 smtp;550 5.7.1 RESOLVER.RST.AuthRequired; authentication required [Stage: CreateMessage]>'
By default, mail-enabled public folders are prevented from accepting mail from external senders. This behavior is by design and is intended to help protect mail-enabled public folders.
To change the behavior so that mail-enabled public folders can accept mail from external senders, follow these steps:
- Connect to Exchange Online by using remote PowerShell. For more info about how to do this, see Connect to Exchange Online using remote PowerShell.
- Add permission for the Anonymous account to public folders. To do this, run the following command:For example, run the following command:
Add-PublicFolderClientPermission -identity <Public Folder> -User Anonymous -AccessRights CreateItems
Add-PublicFolderClientPermission –identity “\SpecificFolder” –User Anonymous –AccessRights CreateItems