Python: when sending email, always blocked in the clause: smtpserver = smtplib.SMTP(“smtp.gmail.com”,587)

Question

I am writing a Python program to send an email. But every time when executing the clause:

smtpserver = smtplib.SMTP(\"smtp.gmail.com\",587)

Answer 1

For reference, cpython smtplib is blocking. That is, it blocks the GIL (ie Python) while connecting. Despite the claims the GIL is released on I/O, it is only released on some I/O, and SMTP connections are not such. To make it async, you need to hand the mail send to another process or thread, depending on your situation.

Answer 2

There may be some issue with the connection (maybe it is being blocked by your proxy or firewall?) and the timeout may be pretty big for you to do not see it going further.

The documentation of smtplib.SMTP says:

class smtplib.SMTP([host[, port[, local_hostname[, timeout]]]])

(...) An SMTPConnectError is raised if the specified host doesn’t respond correctly. The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt (if not specified, the global default timeout setting will be used).

Try specifying the timeout yourself:

smtpserver = smtplib.SMTP("smtp.gmail.com", 587, timeout=30)

Answer 3

Maybe I am 4 years late, but this is what worked for me and might help someone else!

server = smtplib.SMTP("smtp.gmail.com", 587, None, 30)

Answer 4

I ran into a similar issue and none of the answers above worked for me. My problem was that since my smtp server uses SSL. I needed to use smtplib.SMTP_SSL instead of smtplib.SMTP. I just posting my full working code below. Make sure to change values of req and email_config before executing.

    req = {
        "email": "to@something.com",
        "subject": "new e-mail from python",
        "body": "Hi,\nI am a bot",
    }

    email_config = {
        "server": "smtp.orange.fr",
        "port": 465,
        "username": "username@orange.fr",
        "password": "mypassword",
        "email": "fromwhichemail@orange.fr",
    }

#!/usr/bin/env python3
import smtplib

from email import encoders
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText

class Mail(object):
    def __init__(self, email_config):
        self.email = email_config["email"]
        self.password = email_config["password"]
        self.server = email_config["server"]
        self.port = email_config["port"]
        print(f"Logging to {self.server}:{self.port}")
        session = smtplib.SMTP_SSL(self.server, self.port)
        print(f"Calling ehlo")
        session.ehlo()
        print(f"Calling login")
        session.login(self.email, self.password)
        self.session = session

    def send_message(self, subject, to, body, filename):
        # Create a multipart message and set headers
        message = MIMEMultipart()
        message["From"] = self.email
        message["To"] = to
        message["Subject"] = subject
        message["Bcc"] = ""
        # Add body to email
        message.attach(MIMEText(body, "plain"))
        print(f"tot: {to}")
        print(f"subject: {subject}")
        print(f"body: {body}")

        if filename is not None:
            # Open PDF file in binary mode
            with open(filename, "rb") as attachment:
                part = MIMEBase("application", "octet-stream")
                part.set_payload(attachment.read())
            # Encode file in ASCII characters to send by email
            encoders.encode_base64(part)
            # Add header as key/value pair to attachment part
            part.add_header(
                "Content-Disposition",
                f"attachment; filename= {filename}",)
            # Add attachment to message and convert message to string
            message.attach(part)

        # Send e-mail
        print(f"Sending e-mail...")
        self.session.sendmail(self.email, to, message.as_string())

if __name__ == "__main__":
    req = {
        "email": "to@something.com",
        "subject": "new e-mail from python",
        "body": "Hi,\nI am a bot",
    }

    email_config = {
        "server": "smtp.orange.fr",
        "port": 465,
        "username": "username@orange.fr",
        "password": "mypassword",
        "email": "fromwhichemail@orange.fr",
    }
    m = Mail(email_config)
    if "pdf_file" in req:
        m.send_message(req["subject"], req["email"], req["body"], req["pdf_file"])
    else:
        m.send_message(req["subject"], req["email"], req["body"], None)