| Variable | Description |
| TELNYX\_API\_KEY | Your Telnyx API Key |
| TELNYX\_PUBLIC\_KEY | Telnyx Public Key |
| TELNYX\_S3\_BUCKET | The name of the bucket to upload the media attachments |
| TELNYX\_FAX\_CONNECTION\_ID | The connection ID for your Fax Applications |
| MAILGUN\_API\_KEY | Your Mailgun API Key |
| MAILGUN\_DOMAIN | Your Mailgun Domain. |
| PORT | Defaults to 8000 The port the app will be served |
| Callback Type | URL |
| Fax Callbacks | `{ngrok-url}/faxes` |
| Email Callbacks | `{ngrok-url}/email/inbound` |
fax.received webhook for inbound faxes
3. Extract the to/from and other information about the fax
4. Download the attachment and save locally
5. Lookup the association between phone\_number and email
6. Create and send an email via Mailgun with downloaded media as an attachment
#### Sending fax
1. Receive webhook from mailgun for incoming email
2. Extract the prefix of the email ([19198675309@MAILGUN\_DOMAIN.com](mailto:19198675309@MAILGUN_DOMAIN.com), we want 19198675309) and prepend the +
3. Lookup the association between email and phone\_number to determine the from phone number.
4. Save the first attachment locally
5. Upload the attachment to S3
6. Create and send a fax to the phone number extracted above
### Update "DB"
The app as provided uses a dumb-hard-coded database to minimize dependencies for the sake of examples. There is an in memory database defined at the top that associates an email to a Telnyx number.
```
DB = [
{
"email": "@telnyx.com",
"phone_number": "+"
}
]
```
* phone\_number is a **Telnyx** phone number
* email is the email to associate with that phone number
#### Receiving faxes
```
{+19198675309} ==(faxes)==> {telnyx_phone_number} ==(emails)==> {email_as_defined}
```
#### Sending faxes
```
{email_as_defined} ==(emails)==> {destination_phone_number@MAILGUN_DOMAIN} ==(faxes)==> {destination_phone_number}
```
### Launch the app and update callbacks
Start the server python app.py
When you are able to run the server locally, the final step involves making your application accessible from the Internet. So far, we've set up a local web server. This is typically not accessible from the public internet, making testing inbound requests to web applications difficult.
The best workaround is a tunneling service. They come with client software that runs on your computer and opens an outgoing permanent connection to a publicly available server in a data center. Then, they assign a public URL (typically on a random or custom subdomain) on that server to your account. The public server acts as a proxy that accepts incoming connections to your URL, forwards (tunnels) them through the already established connection and sends them to the local web server as if they originated from the same machine. The most popular tunneling tool is ngrok.
Check out the [ngrok setup](/development/development-tools/ngrok-setup/index#ngrok "ngrok setup") walkthrough to set it up on your computer and start receiving webhooks from inbound faxes to your newly created application.
Once you've set up ngrok or another tunneling service you can add the public proxy URL to your Inbound Settings in the Mission Control Portal. To do this, click the edit symbol \[✎] next to your Fax Profile. In the "Inbound Settings" > "Webhook URL" field, paste the forwarding address from ngrok into the Webhook URL field. Add faxes to the end of the URL to direct the request to the webhook endpoint in your server.
For now you'll leave “Failover URL” blank, but if you'd like to have Telnyx resend the webhook in the case where sending to the Webhook URL fails, you can specify an alternate address in this field.
Once everything is setup, you should now be able to:
* Fax your phone number and receive an email
* Email `{19198675309}@domain.com` an attachment to send a fax to `{19198675309}`