[Users] Managing custom email headers

[Jerry]

For some reason I am quite intrigued by custom mail headers.
As far as I understand, Claws Mail is one of the most geeky email
client, if not THE most geeky of all, so I guess it should support at
least some advanced header management.
I have a couple of questions for you:
1) can custom headers for outgoing emails be set on a per-account basis?
2) does Claws mail's Python scripting have access to email headers? In
particular, can a Python script generate custom headers for outgoing
emails?

In case these features are not supported, do you know of any other
email client that supports them?

Thanks

josh