You have an unmoderated List and when a message was posted to the List it was sent out to the List's recipients as soon as it was posted. You are trying to find a way to recall the message that was posted so that recipients who have not opened the message are unable to open the message or get a notification stating that the message has been recalled.
Recalling a message posted to a List is a feature that is not available on LM. However, if the mailing has not finished sending you could stop the mailing in the Outgoing queue but any messages already sent cannot be recalled.
Stop a Mailing in Progress (Will Not Recall Messages Already Sent)
- Log on to LM as an Administrator or List Admin
- Navigate to Mailings > View Outgoing Mailing > Mail Queue
- Locate the mailing in the list and click the Stop Mailing button for the mailing that you want to stop
NOTE: Once a mailing is stopped it cannot be resent.
After stopping the mailing recipients who have not been attempted do not receive the mailing and recipients that were tried but experienced a transient failure can either be deleted or marked as Success or Failure. Deleting a recipient ensures that their attempts have no effect on reports or bounce counts (as if they were never attempted). A success would be useful for a mailing that has been in retry mode for only a short time (i.e. several hours), and the majority of remaining recipients would most likely succeed. A failure would be useful for a mailing that has been in retry mode for a long time (i.e. several days), and it does not look like the remaining recipients will succeed.