Please note this feature is only available in PoliteMail 5.0.
You are allowed to edit message details on already sent emails such as Tag Groups and Send Counts (Aggregate Measurement only). To edit details go to POLITEMAIL > Messages and select the message you wish to update by single-clicking on it. Now go to Actions > Edit Message Details.
The edit dialog box will open on the left and you can update details. Click Save when finished.