Comment 8 for bug 1525048

I see we have an add_frozen method. Maybe all you really want is a remove_frozen method. (Although the del frozen_set['subject'] *does* work - and is exactly what a remove_frozen would do.)

In the remove_frozen method, I could raise an exception if you try to remove 'from', with an i_know_what_i_am_doing=True parameter to not raise the exception.

However, having more than one Subject or Date is a violation of the mail RFCs, not just DKIM. Do we really want to make it easy? The legitimate application of remove_frozen would be for additional headers that were added by the application. It should probably require the i_know_what_i_am_doing flag for removing any of from,subject,date.