View & check the headers and attachment filename(s) of an EML file.

msg_header_checker.py

#!/usr/bin/env python3
from email.header import decode_header


def check_items(msg_):
    """Extract header items from a msg object and Display them.
    Args:
        msg_ (email.message.Message)
    """
    decoded_header = decode_header(msg_.get('subject'))[0]  # (b'\x##', 'utf-8')
    subject_string, apparent_encoding = decoded_header  # Unpack the tuple
    
    if apparent_encoding is None:  # Plain text
        sj = subject_string
    else:  # if base64 encoded
        sj = subject_string.decode(apparent_encoding)
    dt = msg_.get('date')
    fm = msg_.get('from').replace('"', '')
    to = msg_.get('to').replace('"', '')
    cc = msg_.get('cc').replace('"', '') if msg_.get('cc') else ''
    bc = msg_.get('bcc').replace('"', '') if msg_.get('bcc') else ''
    ir = msg_.get('in-reply-to') if msg_.get('in-reply-to') else ''

    header_items = dict(SUBJ=sj, DATE=dt, FROM=fm, TO=to, CC=cc, BCC=bc, IRTO=ir)
    filenames = [i.get_filename() for i in msg_.get_payload() if i.get_filename()]
    # Display
    for k, v in header_items.items():
        print(f'{k:4s}: {v}')
    print(f"ATCH: {'0x0A'.join(filenames)}")


if __name__ == '__main__':
    check_items(msg)