assumes that To, Cc, Bcc hdr values are lists of 1 or more already
decoded addresses (possibly in full name+ format); client
must parse to split these on delimiters, or use multiline input;
note that SMTP allows full name+ format in recipients;
4E: Bcc addrs now used for send/envelope, but header is dropped;
4E: duplicate recipients removed, else will get >1 copies of mail;
caveat: no support for multipart/alternative mails, just /mixed;
"""

4E: assume main body text is already in desired encoding;

clients can decode to user pick, default, or utf8 fallback;

either way, email needs either str xor bytes specifically;

if fix_text_required(bodytextEncoding):
if not isinstance(bodytext, str):
bodytext = bodytext.decode(bodytextEncoding)
else:
if not isinstance(bodytext, bytes):
bodytext = bodytext.encode(bodytextEncoding)

make message root

if not attaches:
msg = Message()
msg.set_payload(bodytext, charset=bodytextEncoding)
else:
msg = MIMEMultipart()
self.addAttachments(msg, bodytext, attaches,
bodytextEncoding, attachesEncodings)

4E: non-ASCII hdrs encoded on sends; encode just name in address,

else smtp may drop the message completely; encodes all envelope

To names (but not addr) also, and assumes servers will allow;

msg.as_string retains any line breaks added by encoding headers;

hdrenc = mailconfig.headersEncodeTo or 'utf-8' # default=utf8
Subj = self.encodeHeader(Subj, hdrenc) # full header
From = self.encodeAddrHeader(From, hdrenc) # email names
To = [self.encodeAddrHeader(T, hdrenc) for T in To] # each recip
Tos = ', '.join(To) # hdr+envelope

add headers to root

msg['From'] = From
msg['To'] = Tos # poss many: addr list
msg['Subject'] = Subj # servers reject ';' sept
msg['Date'] = email.utils.formatdate() # curr datetime, rfc2822 utc
recip = To
for name, value in extrahdrs: # Cc, Bcc, X-Mailer, etc.
if value:
if name.lower() not in ['cc', 'bcc']:
value = self.encodeHeader(value, hdrenc)
msg[name] = value
else:
value = [self.encodeAddrHeader(V, hdrenc) for V in value]
recip += value # some servers reject ['']

962 | Chapter 13: Client-Side Scripting