user_1701 I am in agreenment with whisperer that the F5 should not be used for this purpose. This overcomplicates the configuration and when troubleshooting occurs in the future this will most likely be overlooked and cause even further delays when something needs to be fixed as soon as possible. Just because the F5 can do it doesn't mean it should do it. So the source device isn't something that you control or that it is even a mail server? You really need to speak with the end user that wants this adjustment and have them explain why the source device cannot be corrected to show the correct souce email.