Translation:Not during response and transfer
I would translate this to "Not when answering or forwarding".
Let me try to put this into context: Suppose you have some email program in which you can change the formatting of the text only when you're writing a new email (I agree that would be terrible....). Someone asks you "Kann ich das Textformat ändern wenn ich eine Email beantworte? (Can I change the format when responding to a an email?)" Then you might answer: "Nein, nicht beim Antworten und Weiterleiten" -- "No, not when answering and forwarding".
Of course, "Weiterleiten" can mean "passing on" in other contexts, and I'm sure in this sentence it can also mean "passing on".