Email Alerts

This page covers the SMTP alert sent when an IP joins the Deny list, custom subject and body, and the connection limits that come from net/smtp.

When It Fires

Only Deny.Add sends mail, asynchronously in a goroutine after the Redis and list-file writes succeed; nothing is sent when Config.Email is nil. A failed send is only logged and does not change what Add returns.

Configuration

subject := func(ip, reason string) string {
    return "[Sentry] banned " + ip
}

sentry, err := golangIPSentry.New(golangIPSentry.Config{
    Redis: golangIPSentry.Redis{Host: "localhost", Port: 6379},
    Email: &golangIPSentry.EmailConfig{
        Host:     "smtp.example.com",
        Port:     587,
        Username: "alert@example.com",
        Password: "app-password",
        From:     "alert@example.com",
        To:       []string{"ops@example.com"},
        Subject:  &subject,
    },
    Parameter: golangIPSentry.Parameter{
        BlockTimeMin: 5 * time.Minute,
        BlockTimeMax: 24 * time.Hour,
    },
})
if err != nil {
    log.Fatal(err)
}

A custom function returning an empty string falls back to the default. Subject and Body carry json:"-", so a JSON-loaded config must set them in code.

SMTP Limits

Sending uses the standard library smtp.SendMail with PLAIN auth: