How to Quickly Test SMTP Sending

The goal of an SMTP test is usually simple: verify host/port/auth, confirm messages are delivered, and validate subject/body rendering and encoding. This guide provides several practical ways to test quickly.

Method 1: Use this project’s temporary inbox (recommended)

1. Open the homepage and create a temporary email address.
2. Configure your app/script to send a test email to that address.
3. Open the inbox page and verify delivery, subject, sender, and body.

This is great for validating templates, HTML vs plain text, multipart MIME, and encoding issues.

Method 2: Receive with MailHog

If you run MailHog via Docker Compose, point SMTP to MailHog (usually port 1025) and inspect messages in the MailHog Web UI.

Method 3: Send a test email from the command line

For a minimal connectivity check, you can send a simple message using tools like swaks or manually via openssl s_client (useful for TLS debugging). Use only in test environments.

Troubleshooting checklist

• Timeout: check firewall and whether your VPS provider blocks port 25.
• Auth failed: verify username/password and required AUTH method.
• No delivery: verify recipient address and inspect logs.
• Garbled text: ensure UTF-8 and correct MIME charset.

FAQ

Does a passing test guarantee production deliverability?

No. Production deliverability also depends on SPF/DKIM/DMARC, reputation, and recipient policies.