The Problem
OpenCart provides no built-in way to verify that your SMTP mail settings are correct. The only way to know if your configuration works is to place a test order and hope the email arrives. If it doesn't,
you're left guessing — is it the hostname? The port? The password? The encryption?

The Solution
SMTP Test Button adds a one-click testing tool directly into your OpenCart admin mail settings page (System > Settings > Edit > Mail tab). It tests your SMTP configuration in stages and tells you exactly
what works and what doesn't — before you save, and without placing any orders.

How It Works
Click the "Test SMTP Connection" button and the extension runs a staged diagnostic against your SMTP server using the values currently in the form (even unsaved changes):

- Stage 1: Connection — Can the server be reached on the specified host and port?
- Stage 2: EHLO Handshake — Does the server accept the SMTP protocol handshake?
- Stage 3: Encryption — Is STARTTLS or SSL negotiated successfully?
- Stage 4: Authentication — Are the username and password accepted?
- Stage 5: Send Test Email (optional) — Enter a recipient address to send an actual test email and confirm full delivery.

Results are displayed instantly as a color-coded table with clear pass/fail status for each stage. No page reload, no guesswork.

Key Features
- One-click SMTP connection testing from the admin panel
- Stage-by-stage diagnostic with clear success/error messages
- Tests unsaved form values — tweak and re-test instantly without saving
- Optional test email delivery to verify end-to-end functionality
- Specific error reporting: server unreachable, wrong port, encryption mismatch, authentication failed
- Clean integration into the existing Mail settings tab — feels native
- No core file modifications (OCMOD-based)
- No new database tables
- Lightweight — no dependencies beyond OpenCart core

Compatibility

- OpenCart 3.0.x (tested on 3.0.3.8)
- PHP 7.3+
- Works with all SMTP providers (Gmail, Outlook, Amazon SES, Mailgun, custom servers, etc.)
- Supports plain, SSL (ssl://), and TLS (tls://) connections