Cloud-based Message Recall in Exchange Online

Keith_Sauer the scenario when you route even intra-organizational messages out of the service to a smart host then back in again to recipients in your org (e.g. routing out to Exclaimer then back in) currently isn't supported. It doesn't work because when the Recall message leaves the service its MessageClass is converted from IPM.Outlook.Recall to IPM.Note (a standard email message). We only recall based on IPM.Outlook.Recall messages not standard IPM.Note messages. That's how the classic Outlook recall feature works as well. 

We're working on a solution and hope to add support for this intra-organizational EXO -> external smart host -> EXO scenario by end of this year. Meanwhile, the only workaround I can offer at this time is to stop routing out then back in for your intra-organizational email. If intra-organization messages route within the service, it should work.