Out of office doesn't work for external users.

Question

Out of office doesn't work for external users in On-Premises Exchange 2016. I have set RemoteDomain $true. Configured auto reply for a user from exchange managment shell, OWA and outlook. verified the configuration but no luck in auto reply for external domains users. It's only working for internal users.

Answer 1

Hi,

Welcome to the Microsoft forum.

You can try to do the following:

• Run the command: Set-RemoteDomain -AllowedOOFType 'External' -Identity 'Default'. The AllowedOOFType parameter specifies the type of automatic replies or out-of-office (also known as OOF) notifications than can be sent to recipients in the remote domain. About the parameter's detail you could refer to:https://learn.microsoft.com/en-us/powershell/module/exchange/set-remotedomain?view=exchange-ps
• If the first suggestion doesn't work, you can try to set AllowedOOFType to "ExternalLegacy"
• If it still doesn't work,try to run the command: **Set-RemoteDomain "contoso.mail.onmicrosoft.com" -TNEFEnabled $true -AllowedOOFType "InternalLegacy"**This applies to the situation: Exchange Online users cannot view the out-of-office replies of local users. You can refer to: Out-of-office replies and voting options show wrongly - Exchange | Microsoft Learn
• Check if remote domain blocks OOF replies. This setting can be found in Exchange Admin Center > Mail flow > Remote domains.>Edit reply types More details you can refer to:https://learn.microsoft.com/en-us/exchange/troubleshoot/email-delivery/understand-troubleshoot-oof-replies

Answer 2

Great to know that the issue has already been resolved and thanks for sharing the solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to "Accept" the answer : )     

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Issue Symptom: 

Out of office doesn't work for external users in On-Premises Exchange 2016. I have set RemoteDomain $true. Configured auto reply for a user from exchange managment shell, OWA and outlook. verified the configuration but no luck in auto reply for external domains users. It's only working for internal users.

External OOF from Mailbox Server was fine

Resolution: 

The problem may be in the client's Mail Security Gateway, if the OOF is configured correctly, try checking this related configuration. In this case, the Exchange server is sending mail to Fortimail but Fortimail can't deliver it to external users.