Регулярное выражение для удаления имени, адреса, обозначения из текста электронной почты Python

Ниже приведен ответ, который работает для вашего текущего ввода. Код буду иметь необходимо скорректировать при обработке примеров, выходящих за рамки параметров, указанных в приведенном ниже коде.

with open('email_input.txt') as input:

   # List to store the cleaned lines
   clean_lines = []

   # Reads until EOF
   lines = input.readlines()

   # Remove some of the extra lines
   no_new_lines = [i.strip() for i in lines]

   # Convert the input to all lowercase
   lowercase_lines = [i.lower() for i in no_new_lines]

   # Boolean state variable to keep track of whether we want to be printing lines or not
   lines_to_keep = False

   for line in lowercase_lines:
      # Look for lines that start with a subject line
      if line.startswith('subject: [external]'):
         # set lines_to_keep true and start capturing lines
         lines_to_keep = True

      # Look for lines that start with a salutation
      elif line.startswith("regards,") or line.startswith("warm regards,") \
          or line.startswith("best regards,") or line.startswith("hello,"):
          # set lines_to_keep false and stop capturing lines
          lines_to_keep = False

    if lines_to_keep:
        # regex to catch greeting lines
        greeting_component = re.compile(r'(dear.*,|(hi.*,))', re.IGNORECASE)
        remove_greeting = re.match(greeting_component, line)
        if not remove_greeting:
           if line not in clean_lines:
               clean_lines.append(line)


for item in clean_lines:
    print (item)

    # output 
    subject: [external] re: query regarding supplement 73

    yes, an extension until june 22, 2018 is acceptable.
    we had initial discussion with the abc team us know if you would be able to 
    extend the response due date to june 22, 2018.
    responding by june 15, 2018.check email for updates
    please refer to your january 12, 2018 data containing labeling supplements 
    to add text regarding this symptom. we are currently reviewing your 
    supplements and have made additional edits to your label.
    feel free to contact me with any questions.