Accept and Decline buttons missing in a task request

Symptoms

When you send a task request message in Outlook, the recipient's task request doesn't contain the Accept and Decline buttons or have legible task details. This issue can occur for recipients who are internal or external to your Microsoft Exchange organization.

For example, the recipient's task request might resemble the following example.

The next screenshot shows what the task request should look like.

Cause

Outlook sent the task request as a Rich Text Format (RTF) message, but a transport component changed the message format to HTML. The conversion to HTML removed the button elements and scrambled the message layout.

If the recipient is internal to your Exchange organization, your Exchange configuration might have:

• An outbound connector that routes messages through an external service. Internal mail flow preserves the format of RTF messages, but external services often convert RTF messages to HTML. For example, signature and privacy disclaimer services convert RTF messages to HTML.

If the recipient is external to your Exchange organization, your Exchange configuration might have either:

• An outbound connector that routes messages through an external service that changes the message format to HTML.

• A remote domain TNEFEnabled setting that converts outbound RTF messages to HTML.

Resolution

To resolve the issue, check the following settings, and then make the appropriate changes:

• For internal and external recipients, check whether an outbound connector routes messages through an external service. If it does, consider adding an exception to the mail flow rule that routes messages to that connector. For example, you can exclude task request messages from being routed through external services by creating an exception for messages that have a subject that starts with "Task request:".

• For external recipients, check the TNEFEnabled setting for all remote domains. To do this, run the following command:

  Get-RemoteDomain | Where {$_.TNEFEnabled -ne $true}
  

If the TNEFEnabled setting for a remote domain is $null or $false, Exchange will convert RTF messages to HTML for recipients in that domain. For example, if the TNEFEnabled setting for your default remote domain is $null, and if it's your only remote domain, Exchange will convert all external RTF messages to HTML. To fix the issue for an affected external recipient, follow these steps:

1. Create a remote domain for the affected external recipient's domain.

2. Set TNEFEnabled to $true for that domain by running the following command:

   Set-RemoteDomain -Identity <name of the new remote domain> -TNEFEnabled $true
   

Note

Avoid setting TNEFEnabled to $true on the default remote domain because that change will affect all external recipients, including those whose email client might not support RTF messages.