Minimal setup & reliable delivery
Send email in Flask
Add email sending to your Flask app in under 30 minutes with Sidemail's official Python SDK and developer‑friendly API. Sidemail takes care of deliverability, SPF/DKIM/DMARC, templates, and infrastructure so your Flask routes can send emails fast and reliably.
Get startedRead API docsfrom flask import Flask, request, jsonify
from sidemail_client import sidemail
app = Flask(__name__)
@app.post("/register")
def register():
data = request.get_json()
# ... create user in database
sidemail.send_email(
to_address=data["email"],
from_address="[email protected]",
from_name="Your App",
template_name="Welcome",
template_props={"firstName": data["name"]},
)
return jsonify({"status": "registered"})Quickstart: Send email in Flask
Start sending emails from your Flask app in three steps:
Install the Sidemail Python SDK
Add Sidemail to your Flask project via pip:
pip install sidemailCreate a shared Sidemail client
Create a sidemail_client.py module and initialize the Sidemail client. The SDK reads SIDEMAIL_API_KEY from your environment automatically.
# sidemail_client.py
from sidemail import Sidemail
sidemail = Sidemail()Send email from a route
Import the client and call send_email. Pass the recipient, sender, and template or content. That's it.
from flask import request, jsonify
from sidemail_client import sidemail
@app.post("/register")
def register():
data = request.get_json()
# ... create user in database
sidemail.send_email(
to_address=data["email"],
from_address="[email protected]",
from_name="Your App",
template_name="Welcome",
template_props={"firstName": data["name"]},
)
return jsonify({"status": "registered"})Key features & perks
Why Sidemail for Flask emails
Quick Flask email integration
Send emails from Flask routes in minutes. Sidemail's Python SDK and JSON API fit naturally into Flask's micro-framework philosophy. Clear docs and copy‑paste examples get you running in under 30 minutes.Reliable email delivery
Sidemail's solid infrastructure and careful sender vetting process make sure your emails consistently reach inboxes, not spam folders. Dependable delivery without the hassle of managing your own email infrastructure.Custom sending domain with DKIM & SPF
Send from your own domain without complex DNS configuration. Sidemail automatically sets up DKIM and SPF for you — two of the most critical factors for strong inbox delivery and sender reputation.All‑in‑one email platform
Sidemail covers everything in a single platform – transactional and marketing emails, newsletters, email automation, subscriber collection, and contact management. One tool for every email use case.Premade email templates & no‑code editor
Sidemail comes with a library of battle‑tested email templates that look great in every inbox, like for example welcome emails, password resets, account activation emails and more. Need something custom? The no‑code editor lets you build responsive templates from scratch without writing any HTML.Best‑in‑class developer experience
Sidemail's email API is designed for busy developers — clear documentation, copy‑paste code examples in multiple languages, and developer‑focused features that make integration genuinely painless. From markdown email support and detailed delivery logs to an MCP server and rich API data, Sidemail is the email platform developers love using.
Flask transactional email examples
With Sidemail, you can send any transactional email from Flask. Here are a few examples with code:
# Flask: Send an account verification email
from flask import request, jsonify
from sidemail_client import sidemail
@app.post("/register")
def register():
data = request.get_json()
# ... create user, generate token
sidemail.send_email(
to_address=data["email"],
from_address="[email protected]",
from_name="Your App",
template_name="Email Verification",
template_props={
"verifyUrl": f"https://yourapp.com/verify?token={token}",
},
)
return jsonify({"status": "registered"})Verification email
Send a sign-up verification email with a one-time link or code to confirm the user's address.
- Include a clear call-to-action in verification emails and make the verification link expire for security.
- Sidemail provides a ready-made account activation template for this common use case.
# Flask: Send a payment receipt email
from datetime import date
from sidemail_client import sidemail
sidemail.send_email(
to_address=user["email"],
from_address="[email protected]",
from_name="Your App",
template_name="Payment Receipt",
template_props={
"userName": user["name"],
"amount": "$19.99",
"date": date.today().strftime("%b %d, %Y"),
},
)Receipt or notification email
Send a receipt, invoice, or generic notification to your user.
- For receipts or order confirmations, include key details like the amount, date, and items in the email.
- Pass dynamic data via
template_propsto populate Sidemail's receipt and invoice templates.
# Flask: Schedule a welcome email for 1 hour from now
from datetime import datetime, timedelta, timezone
from sidemail_client import sidemail
scheduled_time = datetime.now(timezone.utc) + timedelta(hours=1)
sidemail.send_email(
to_address="[email protected]",
from_address="[email protected]",
from_name="Your App",
template_name="Welcome",
template_props={"firstName": "Alex"},
scheduled_at=scheduled_time.isoformat(),
)Welcome email with scheduled delivery
Schedule a welcome email to be delivered later, for example one hour after sign-up.
- Use the
scheduled_atfield with an ISO timestamp to control exactly when the email is sent. - Ideal for onboarding flows where you want to delay the first message until the user has had time to explore.
# Flask: Send a password reset email with Markdown
from pathlib import Path
from sidemail_client import sidemail
markdown = Path("templates/emails/password-reset.md").read_text()
sidemail.send_email(
to_address="[email protected]",
markdown=markdown,
template_props={
"firstName": "Alex",
"resetLink": "https://yourapp.com/reset?token=abc123xyz",
"expiresIn": "30 minutes",
},
)---
subject: "Reset your password"
fromAddress: "[email protected]"
fromName: "Your App Security"
---
Hi {firstName}, we received a request to reset your password.
[$btn Reset password]({resetLink})
This link expires in {expiresIn}.Password reset email sent with Markdown
Sidemail's API gives you the option to write email content in Markdown, which is automatically transformed into pixel‑perfect, responsive emails that look great in every inbox and on every device. Each email is branded with your logo and styled to match your project's email design.
- Store your password reset email in a
.mdfile in your Flask templates folder - Subject and sender are defined in the markdown frontmatter.
- Pass dynamic values via
template_props(such asresetLinkandexpiresIn), which map directly to variables in your markdown.
Deliverability best practices
SPF, DKIM, and DMARC for transactional email
SPF and DKIM are authentication protocols that verify your emails are legitimately sent from your domain. And DMARC builds on both by instructing mail servers how to handle messages that fail those checks. Together, they are 3 critical factors for inbox delivery and sender reputation.
Sidemail automatically handles SPF, DKIM, and DMARC setup for you, so your Flask app sends authenticated, best‑practice‑compliant emails from the start.
The simplest way to build emails
No‑code email editor & premade email templates
Sidemail's no‑code email editor is the quickest way to create responsive email templates that render correctly across every client and device. No HTML knowledge needed. Add your logo and brand colors, and you're ready to send.
Need to move faster? Sidemail includes a library of production‑ready templates for the most common use cases – password resets, welcome emails, receipts, and more. Build from scratch or customize a premade template — we guarantee your emails look great everywhere.
Learn moreDeveloper‑friendly formatting
Markdown support for Flask emails
Writing and maintaining HTML emails by hand is tedious, especially when you just want to send clean, readable content.
Sidemail lets you write your email body in Markdown and automatically converts it into a responsive, well‑styled HTML email. You get smart formatting – headings, lists, links, and code blocks – without worrying about broken layouts or cross‑client rendering issues.
Ideal for transactional emails sent from your Flask app – clean content, fast authoring, and zero HTML to debug.
Learn more
Get started today
Ready to send transactional emails from your Flask app? With Sidemail's email API and premade templates, you can integrate in under 30 minutes and deliver emails reliably.
Start free trialFAQs
How do I send email in Flask?
The easiest way to send email from a Flask app is by using an email API like Sidemail. Install the Python SDK (pip install sidemail), create a shared client module, and call sidemail.send_email() from any route. No SMTP setup or Flask-Mail extension needed. Sidemail handles authentication, formatting, and deliverability for you.
Do I need Flask-Mail to send email?
No. Sidemail's Python SDK makes direct API calls, so you don't need Flask-Mail or any SMTP server. A single pip install and your API key are all that's required. You get template support, scheduling, delivery tracking, and high deliverability built in — features Flask-Mail doesn't provide.
How do I use email templates with Flask?
Instead of building email HTML with Jinja2, use Sidemail's template system. In the Sidemail dashboard, pick a premade template or build one with the drag‑and‑drop editor. In your Flask route, reference the template by template_name and pass dynamic data via template_props. Sidemail merges the data and sends a well‑formatted email.
Can I send emails from Flask Blueprints?
Yes. Since Sidemail is a plain Python module, you can import it into any Blueprint. Just import the shared client from sidemail_client and call send_email() in any route handler, regardless of which Blueprint it belongs to. No Flask app context coupling required.
Can I send emails asynchronously from Flask?
Sidemail's API responds fast (typically under 200ms), so synchronous calls work well for most routes. If you need non-blocking delivery, call send_email() from a Celery task or RQ job. Alternatively, use Sidemail's scheduled_at field to queue the email for future delivery without a task queue on your end.
How do I handle email errors in Flask?
Wrap your sidemail.send_email() call in a try/except block and catch sidemail.SidemailError. The exception includes the HTTP status code, error type, and a human-readable message. Log it with Python's logging module and return an appropriate response to the client.