Overview
Send transactional emails through Sendfully's SMTP server.
SMTP (Simple Mail Transfer Protocol) is a long-standing protocol used to send emails. If your application, content management system, or framework already supports SMTP, you can point it at Sendfully and start sending right away.
When to use SMTP
SMTP is a good fit when:
- Your platform supports SMTP, for example WordPress, Ghost, or Supabase
- You're migrating from another provider and already have SMTP sending in place
However, the REST API is the recommended way to send transactional emails if you can. It gives you type-safe request validation and structured error responses.
Connection details
| Setting | Value |
|---|---|
| Host | smtp.sendfully.com |
| Port | 465 |
| Username | sendfully |
| Password | Your API key (sf_live_...) |
| Encryption | TLS (implicit) |
Authentication
Every SMTP connection must authenticate. Set the username to sendfully and the password to your API key. You can set up an API key with sending access in your Sendfully dashboard under Settings > API keys.
Treat your API key like a password. Don't commit it to source control or expose it in client-side code.
From address
The from address in your email headers must use a domain you've verified in Sendfully. If the domain doesn't match, the send will be rejected.
You can include a display name using the standard format: Display Name <email@yourdomain.com>.
Recipients
You can include recipients in the To, Cc, and Bcc fields. Every message needs at least one To recipient. Each recipient counts as one email towards your plan's sending limit.
Attachments
To include an attachment, add it to your message using your SMTP library's attachment API. The total message size, including all attachments, can be up to 40 MB. Certain executable file types (e.g., .exe, .bat) are blocked for security.
Custom headers
If your SMTP client supports custom headers, you can add them to your emails. Standard headers like From, To, Subject, and Reply-To are handled by Sendfully automatically, so only non-standard headers are passed through to the recipient.
Some common use cases:
List-Unsubscribelets email clients show a native unsubscribe button in the inboxX-Entity-Ref-IDprevents Gmail from threading unrelated emails together (useful for notifications that share the same subject line)
What's next?
- Node.js with Nodemailer - send emails using Nodemailer
- Python with smtplib - send emails using Python's standard library
- Getting started with transactional emails - create templates and send via the REST API
- Sending domain - verify your domain before sending