Connection to SMTP server not closed after exception

[chamalsl]

Django EmailMessage class does not close connection to SMTP server, when an exception is raised.

     email_msg = EmailMessage(subject="Topic\n", body="Body", from_email="chamals@test.com",
                             to=["chamaltest@test.com"])
     email_msg.send()

Above Django/python code sends an email. But the email's subject contains a new line.
So Django will raise a BadHeaderError. But the connection to the SMTP server is not closed.

Steps

1. Create a Django app. Add this method to a view.

     def email(request):
       email_msg = EmailMessage(subject="Topic\n", body="Body", from_email="chamals@test.com",
                               to=["chamaltest@test.com"])
       email_msg.send()
       return HttpResponse("Sent")
   

• Note: There is a new line character in the email subject.

2. Install aiosmtpd

    python3 -m pip install aiosmtpd
   

3. Run smtpd server This will start a SMTP server on port 8025

    python3 -m aiosmtpd -n
   

4. Add these lines to settings.py of your Django app.

      EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'
      EMAIL_HOST = 'localhost'
      EMAIL_PORT = 8025
   

5. Open attached send_emails.py Change URL in this line to match your application's URL.

    requests.get('http://localhost:8080/file/email')
   

6. Run send_emails.py This script will make 10 requests to send email.

   python3 send_emails.py
   

7. Check connections to port 8025 (SMTP server)

   netstat -at | grep 8025
   

You can see some connections are in ESTABLISHED state.

8. Remove the new line character inside the "def email" method. Run send_emails.py. Then run

    netstat -at | grep 8025.
   

You will see all connections are in TIME_WAIT state.

[chamalsl]

I am unable to attach send_emails.py, because it is detected as spam.
This is the code for send_email.py.

import requests
i = 0
times = 10
while i < times:
  requests.get('http://localhost:8080/file/email')
  i = i+1
print('Completed')

[Mariusz Felisiak]

Fixed in 8a844e761d098d4005725f991a5e120a1f17cb70.