Python smtplib error when creating smtp(): 'utf-8' codec can't decode byte

Question

I can't solve the problem of sending an email in any way with gmail.com , neither with mail.ru(bk.ru): when creating SMTP, even empty, this error occurs I use PyCharm 2020.1

import requests
import smtplib                                      # Импортируем библиотеку по работе с SMTP

from email.mime.multipart import MIMEMultipart      # Многокомпонентный объект
from email.mime.text import MIMEText                # Текст/HTML
from email.mime.image import MIMEImage              # Изображения

addr_from = "zabrell@bk.ru"                 # Адресат
addr_to   = "zabrell@bk.ru"                   # Получатель
password  = "***"                                  # Пароль

msg = MIMEMultipart()                               # Создаем сообщение
msg['From']    = addr_from                          # Адресат
msg['To']      = addr_to                            # Получатель
msg['Subject'] = '1'                   # Тема сообщения
body = '1'
msg.attach(MIMEText(body, 'plain'))                 # Добавляем в сообщение текст

server = smtplib.SMTP_SSL('smtp.mail.ru', 465)      # Создаем объект SMTP
server.login(addr_from, password)                   # Получаем доступ
server.send_message(msg)                            # Отправляем сообщение
server.quit()                                       # Выходим

If I replace

server = smtplib.SMTP_SSL('smtp.mail.ru', 465)

with

server = smtplib.SMTP_SSL() 
server.connect('smtp.mail.ru', 465)

and even without _SSL(but it no connection on the server), then this error still comes out at the stage smtplib.SMTP_SSL()

Traceback (most recent call last):
  File "C:/Users/zabre/PycharmProjects/miners_test/script.py", line 35, in <module>
    server = smtplib.SMTP_SSL('smtp.mail.ru', 465)      # Создаем объект SMTP
  File "C:\Users\zabre\AppData\Local\Programs\Python\Python38-32\lib\smtplib.py", line 1034, in __init__
    SMTP.__init__(self, host, port, local_hostname, timeout,
  File "C:\Users\zabre\AppData\Local\Programs\Python\Python38-32\lib\smtplib.py", line 263, in __init__
    fqdn = socket.getfqdn()
  File "C:\Users\zabre\AppData\Local\Programs\Python\Python38-32\lib\socket.py", line 756, in getfqdn
    hostname, aliases, ipaddrs = gethostbyaddr(name)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf7 in position 10: invalid start byte

Process finished with exit code 1

I understand the meaning of the error, but it looks like it's somewhere inside the smtplib itself - and this puts me in a confusion

Answer 1

The library tries to use socket.getfqdn() to find out the local host name to send to the remote server:

...
    if local_hostname is not None:
        self.local_hostname = local_hostname
    else:
        # RFC 2821 says we should use the fqdn in the EHLO/HELO verb, and
        # if that can't be calculated, that we should use a domain literal
        # instead (essentially an encoded IP address like [A.B.C.D]).
        fqdn = socket.getfqdn()
        if '.' in fqdn:
            self.local_hostname = fqdn
...

So the question is: what is your hostname? The problem might be that it contains non-ascii characters and fails to be decoded as UTF-8.

One possible solution, besides changing the hostname, would be to explicitly pass the local_hostname in the constructor:

server = smtplib.SMTP_SSL('smtp.mail.ru', 465, 'your.host.name')