Hi @sls89, thanks for making the changes. Some tests broke like test_name_field_not_included_in_envelop_addresses, can you have a look at them?

I think it's because you did not hide this behavior behind a flag like in David Ford's proposal (https://bugs.python.org/issue29539#msg287662). This is not backward compatible and I don't think the new feature can be accepted as is. Can you add new new parameter so this new feature is disabled by default and can be opted-in?