class Mail::Field

def split(raw_field) #:nodoc:
  if raw_field.index(Constants::COLON)
    name, value = raw_field.split(Constants::COLON, 2)
    name.rstrip!
    if name =~ /\A#{Constants::FIELD_NAME}\z/
      [ name.rstrip, value.strip ]
    else
      Kernel.warn "WARNING: Ignoring unparsable header #{raw_field.inspect}: invalid header name syntax: #{name.inspect}"
      nil
    end
  else
    raw_field.strip
  end
rescue => error
  warn "WARNING: Ignoring unparsable header #{raw_field.inspect}: #{error.class}: #{error.message}"
  nil
end