Permissions question

I have noticed that Kmail gives attachments the following permissions: -rw-r--r--. For instance, I sent myself a C binary. It left as -rwxr-xr-x but the when it arrivied, the permissions were -rw-r--r--. Is this a feature of just Kmail or do all linux MUA's (Pine, Mutt, Balsa ...) do this? -- Cheers, Jonathan