You will only see your API key if you log in as a user account on the frontend, if you impersonate a customer account as a backend admin the API key will be blank.
In the email marketing platform, go to Integrate -> API & SMTP -> SMTP Relay
The free version of the Cloudflare proxy is incompatible with incoming SMTP.
Use the IP address instead of the domain for incoming SMTP with Cloudflare enabled.
If you enable the Cloudflare proxy, all non HTTP/HTTPS traffic is blocked unless you pay for the spectrum service. You can also use an unproxied subdomain here instead of the IP. Outgoing SMTP Relay will always continue to work normally.
Attachments are currently not supported for transactional mail
Image attachments will be removed automatically, you need to include images by using regular HTML the usual way.
Configure your sending application to use your ESP hostname or IP address and ports 587, 2525, or 8025.
To make a secure encrypted connection, use the TLS extension after connecting via regular SMTP. SSL method is not supported.
If a multipart message consists of text and HTML parts, only HTML will be used.
Text parts are unsupported.
Use your API Key for your username and password.
The following standard headers are valid in a transactional message.
From: The from name and from email address, aka the 'Friendly From' or 'From Name'.
To: Specify the recipient's name but not their email address.
Subject: The message subject line.
Reply-To: Include an optional Reply-To address.
The following platform-specific headers are valid in a transactional message.
X-Transactional-Tag: If left blank, the message will be tracked as “untagged” on the transactional dashboard.
X-Transactional-Route: Specifies a postal route to use. This is required if the customer account has more than one postal route available, otherwise, the message will fail.
X-Transactional-Template: Include a template ID if you want to send this message using a pre-created transactional template.
X-Auth-APIKey: Bypass the SMTP AUTH username and password method and authenticate via header instead.
X-Transactional-Variables: Specifies a JSON string to use as an input dictionary for the Jinja2 templating system. For more details on Jinja2 see our API docs.
All other headers are automatically discarded and ignored.
You can actually use whatever you want for the Transactional SMTP Relay username. We recommend using the API Key for the username and password for simplicity of explanation, but the username is actually ignored and discarded and can be anything.