Hi @dwhi ,
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but also learned that it is very rare for the recall to actually be carried out successfully.
As I know, the success or failure of a message recall depends on the recipients' settings in Outlook. For more information, please refer to the following article which mentions five scenarios about that: To check on the recall.
at which point is the replacement sent?
The replacement message will be sent after you choose "Delete unread copies and replace with a new message">click OK>edit the replacement message>send, whether you recall the original message successfully or not.
Is that the case or will there potentially be two emails in the recipients inbox, the failed recall and the replacement one?
If recall fails, there will be original and replacement messages in the recipient's inbox. If recall succeeds, there will be only replacement message in the recipients inbox. To check if the original message can be successfully recalled, please refer to the documents mentioned at the beginning of this reply.
Hope the above help.
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