SMTP Support
TLS / STARTTLS, authentication, and per-message context cancellation
Templating
Go html/text templates for HTML and plain-text email bodies
Attachments
Send files with proper MIME encoding and content types
Retry Logic
Configurable exponential backoff for transient SMTP failures
Rate Limiting
Built-in token-bucket limiter to avoid overwhelming providers
Connection Pooling
Reuse SMTP connections for high-throughput sending
Async Sending
Background queue with configurable workers and buffer size
Middleware Pipeline
Composable logging, metrics, recovery, and lifecycle hooks
Provider Adapters
SendGrid, Mailgun, and AWS SES via HTTP APIs (separate modules)
DKIM Signing
RSA-SHA256 / Ed25519 signing per RFC 6376 + 8463 — zero extra deps
Webhooks
Receive and normalize delivery events from any provider
Pluggable Logger
Bring your own logger — slog, zap, logrus, zerolog, anything
Mock Sender
Drop-in test double with assertions on sent messages
Header Safety
Automatic header-injection protection and address validation
Why goemail?
net/smtp gets you a connection and a DATA command. Everything past that — the parts that turn “I can send one email” into “I can run this in production” — is what goemail provides. It is not a replacement for net/smtp; the default Sender is built on top of it.
| Capability | goemail | Raw net/smtp |
|---|---|---|
| Retry with exponential backoff | Included | You build it |
| Connection pooling for high throughput | Included | You build it |
| Rate limiting | Included | You build it |
| DKIM signing (RSA-SHA256 / Ed25519-SHA256) | Included | You build it |
| HTML templates, attachments, batch sending | Included | You build it |
| Provider HTTP adapters (SendGrid, Mailgun, AWS SES) | Included | You build it |
| Middleware (logging, metrics, hooks, recovery) | Included | You build it |
| Header injection protection, address validation | Included | You build it |
| Async sending with a buffered worker queue | Included | You build it |