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AhaSend lets you send transactional email from Azure Functions in Python through the HTTP API; this guide adds a protected function with a local test.

Prerequisites

Use a verified sending domain, your account ID, and a domain-scoped send-only API v2 key. Use sandbox mode for every test. Management tasks need a separate full API key. Use Python 3.13, Azure Functions Core Tools v4 and the Python v2 programming model.

Install the Dependencies

Try a Sandbox Send

Set AHASEND_API_KEY, AHASEND_ACCOUNT_ID and AHASEND_FROM in your shell or local secret store. Use a send-only key and an address on your verified domain. Save this as quick_send.py:
quick_send.py
Run python quick_send.py in the activated environment. It prints acceptance statuses and exits with an error if sending fails. Sandbox acceptance does not deliver mail. The production version below adds input checks and a stable request key.

Add the Shared Sending Code

Save this as send_email.py beside the function file. It uses Python’s standard library, so this example needs no SDK package. Set AHASEND_API_KEY, AHASEND_ACCOUNT_ID, AHASEND_FROM, AHASEND_TO and SEND_TOKEN in the runtime environment. Use a long random SEND_TOKEN for requests from your trusted server. For the first run set AHASEND_TO=recipient@example.com and AHASEND_DELIVERY_MODE=sandbox; keep a sandbox credential in place while testing. Set live only when ready to deliver to your own approved recipients.
send_email.py
Only your server chooses the sender, recipient and message body. Look up a user’s verified address from your database before adapting this to a real signup flow. Keep that saved message unchanged when retrying an event_id; a new business event needs a new ID. See idempotency for time limits and uncertain outcomes. Record an internal event ID on failures without logging API keys or message bodies. Add request limits at the hosting layer.

Create the HTTP Function

Save this as function_app.py:
function_app.py
Create host.json:
host.json

Run with Core Tools

Activate .venv, export the variables from the shared code, and run:
Keep secrets, .venv and local.settings.json out of Git. In another shell with SEND_TOKEN set, run:
Expect HTTP 202 with acceptance statuses. Invalid JSON or event IDs return 400; a wrong bearer token returns 401. Use a new event ID for a new test and the original ID for a retry of the same message. Local Core Tools does not enforce function keys; the bearer check still runs.

Prepare the Hosted App

Select Python 3.13 on a supported Linux Functions plan. Include requirements.txt, host.json, function_app.py and send_email.py in the project. Keep secrets in Key Vault references and ordinary configuration in app settings. Add x-functions-key to hosted requests alongside the bearer token. Follow Microsoft’s Python deployment guidance and enforce your application’s permissions and request limits. Track final delivery with webhooks. Also see Azure in Node.js, Azure in Go and Python SMTP.