Microsoft Flow sends actionable messages to approval recipients so that they may respond to the requests directly from their inbox. For an overview of actionable messages, see the following documentation: Actionable messages in Outlook and Office 365 Groups. For the minimum versions of Office that support actionable message, see the Release Notes.
Actionable Messages must be enabled at the O365 tenant level for any users to receive them. To ensure the options are enabled, use the following O365 PowerShell command and verify that both options are set to $true:
Get-OrganizationConfig | ft ConnectorsActionableMessagesEnabled,SmtpActionableMessagesEnabled
For users that are not on the required version of Outlook, or are using another mail client like Mail.app for iOS/Mac OS X, etc., users will receive an HTML email with links to take the user to the Flow portal to respond to approvals.
The Actionable Messages Debugger can help reveal common causes of issues with actionable messages. Installing this tool adds a button within Outlook Desktop and Web that will show diagnostic and error information.
Customers may run into a few issues regarding receiving and approving approval messages directly from within Outlook.
1. Neither Outlook Desktop nor Outlook Web (OWA) give the user actionable responses.
This typically means that a user is not using a supported version of Office 365, or mail for the specific account is being redirected to an on-premises mail server. See Release Notes for more details. Alternatively, actionable messages may be disabled at the tenant level (see above for how to check this).
This situation can also arise if there are SMTP mail delays between Microsoft Flow and the user's mailbox of over an hour (more frequently possible when a tenant is using a filtering service that receives mail before routing it to Office 365). The Actionable Messages Debugger will show a diagnostic message similar to:
Message card signature validation failed - iat validation failure, card was processed 70 minutes from IAT
2. Outlook Desktop does not present actionable messages, but Outlook Web (OWA) does.
This is a known issue fixed in Outlook Desktop builds 1911(16.0.12228) and higher, involving user permissions accessing the Office Add-in store. A temporary workaround is to make sure that the affected users have access to the Office Store for Add-ins (though this is temporary and will not be necessary after Office desktop release). To verify this case, look for the following registry key. If empty, the user does not have access to the Office store and will not receive actionable emails in Outlook Desktop.
3. Users receive a message similar to "Sorry, an error occurred. Please try again later" when responding to messages from Outlook Desktop.
This is a known issue fixed in the June release train of Outlook Desktop, build version 16.0.11901.20167 and higher. The workaround in the meantime is to use Outlook Web (OWA).