Everything you need to know to configure a connecting application to send email through your platform using transactional SMTP Relay
Add the Postal Route to the Customer Account
Log in as the User Account in Incognito mode or a second web browser
You have to log in directly as the User for this next step.
Don't use administrator impersonation mode.
Find your User API Key by clicking Integrate -> API & SMTP -> SMTP Relay
Use the API Key as your username and password
Connect to your ESP platform DNS hostname or IP address on port 587, 2525, or 8025
Use STARTTLS or TLS for your encryption method, or choose no encryption
All three ports accept both TLS and disabled/no encryption.
TLS is the only supported encryption method - do not select SSL in your application.
Try connecting using your IP address instead of your domain if you run into issues.
Your transactional SMTP messages will be delivered via the Customer's Postal Route.
Mail comes into your Transactional SMTP Relay on port 587, 2525, or 8025 and goes out of the Connection or MTA Policy configured in the Postal Route assigned to your Customer Account in the administrative backend.
All mail delivered from your ESP platform follows the same pathway:
Broadcast, Funnel, or Transactional Message -> Customer Account -> Postal Route -> API Connection, SMTP Relay Connection, or MTA Policy -> Gmail/Yahoo/Outlook/etc
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.
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.