Sending Emails with smtplib

Security note

Don’t hardcode passwords.

Prefer:

app passwords
environment variables
secret managers

Plain text email

smtp_plain.py

import os
import smtplib
from email.message import EmailMessage
 
SMTP_HOST = "smtp.gmail.com"
SMTP_PORT = 587
 
 
def send_email(to: str, subject: str, body: str):
    user = os.environ["SMTP_USER"]
    password = os.environ["SMTP_PASS"]
 
    msg = EmailMessage()
    msg["From"] = user
    msg["To"] = to
    msg["Subject"] = subject
    msg.set_content(body)
 
    with smtplib.SMTP(SMTP_HOST, SMTP_PORT) as smtp:
        smtp.starttls()
        smtp.login(user, password)
        smtp.send_message(msg)
 
 
# send_email("to@example.com", "Hello", "Test")

smtp_plain.py

import os
import smtplib
from email.message import EmailMessage
 
SMTP_HOST = "smtp.gmail.com"
SMTP_PORT = 587
 
 
def send_email(to: str, subject: str, body: str):
    user = os.environ["SMTP_USER"]
    password = os.environ["SMTP_PASS"]
 
    msg = EmailMessage()
    msg["From"] = user
    msg["To"] = to
    msg["Subject"] = subject
    msg.set_content(body)
 
    with smtplib.SMTP(SMTP_HOST, SMTP_PORT) as smtp:
        smtp.starttls()
        smtp.login(user, password)
        smtp.send_message(msg)
 
 
# send_email("to@example.com", "Hello", "Test")

Visualize it

Sending an email with smtplib follows a straightforward compose-connect-send sequence.

diagram Email sending flow mermaid

  flowchart LR
    A["Compose message (subject, body, attachments)"] --> B["Connect to SMTP server (TLS)"]
    B --> C["Log in"]
    C --> D["Send"]
    D --> E["Close connection"]

Steps smtplib takes to compose and deliver an email

🧪 Try It Yourself

Exercise 1 – List Files with os.listdir

Exercise 2 – Join Paths with os.path.join

Exercise 3 – Write and Read a File

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