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Mail SMTP by Oi

A SMTP plugin for WordPress by Oi

by Oi Technologies · github.com/oiencrypted/mail-smtp-by-oi · website

★ 0stars

Install

Download source zip No release zip yet

This is the repository archive. It installs, but the folder name will carry the branch suffix and updates will not flow.

Install straight from GitHub with WP-CLI:

wp plugin install https://github.com/oiencrypted/mail-smtp-by-oi/archive/refs/heads/main.zip
No built-in updater. New versions won't appear under Dashboard → Updates. Install new releases yourself, or let Git Updater track the repository.
Readme github.com/oiencrypted/mail-smtp-by-oi ↗

Mail SMTP by Oi 🚀

The Ultimate High-Performance SMTP & Transactional Email Plugin for WordPress
Fix WordPress email deliverability forever. Connect Custom SMTP, Gmail, Outlook, SendGrid, Mailgun, Brevo, Postmark, and Resend with comprehensive email logging, 1-click resend, and live diagnostics.

WordPress 5.6 - 7.0+ WooCommerce Compatible PHP 7.4 - 8.3+ GPL v3 License Security AES-256-CBC Oi Technologies

Why Mail SMTP? • Key Features • How It Works • Supported Providers • Installation • Provider Guides • Email Logger • Diagnostics • Security • FAQ • About Oi

⭐ If this plugin solves your WordPress email deliverability problems, please consider starring the repository — it helps other developers and store owners discover it!

📖 Why Mail SMTP by Oi? (কেন এই প্লাগইন?)

By default, WordPress attempts to send emails using the web server's native PHP mail() function. This causes critical business issues:

  • ❌ No Authentication: Emails lack SPF, DKIM, and DMARC alignment, causing Gmail, Yahoo, and Outlook to flag them as Spam or reject them completely.
  • ❌ Silent Failures: Web hosts often disable or throttle mail(), leaving you unaware that order notifications, password resets, or form submissions never reached their destination.
  • ❌ Bloated Alternatives: Most existing SMTP plugins are bloated with slow tracking scripts, heavy vendor SDKs, aggressive upsells, and locked features.

Mail SMTP by Oi was built from the ground up by Oi Technologies to provide an ultra-clean, lightweight, high-performance, and feature-complete solution that respects your server resources and privacy.

📊 Comparison Table

Feature Default WordPress mail() Generic SMTP Plugins Mail SMTP by Oi
Delivery Reliability 🔴 Low (often Spam) 🟡 Medium 🟢 100% In-Box Delivery
Custom SMTP (cPanel/Postfix) ❌ No 🟢 Yes 🟢 Yes (SSL/TLS/AutoTLS)
Direct Cloud APIs (No Bloat) ❌ No 🟡 Locked in Pro 🟢 SendGrid, Resend, Brevo, Mailgun, Postmark
Full Email Logger ❌ No 🟡 Paid Add-on 🟢 Built-in Free
1-Click Email Resend ❌ No 🟡 Paid Add-on 🟢 Built-in Free
Live SMTP Handshake Terminal ❌ No ❌ No 🟢 Real-time Live Debugger
Outbound Port Diagnostic Scanner ❌ No 🟡 Basic 🟢 Ports 587, 465, 2525, 25
SPF & DMARC DNS Analyzer ❌ No ❌ No 🟢 Built-in Free
Credential Storage Security N/A 🔴 Plain text in DB 🟢 OpenSSL AES-256-CBC Encrypted
Performance Impact N/A 🔴 Heavy SDKs 🟢 Ultra-Lightweight & Fast
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✨ Key Features (মূল সুবিধাসমূহ)

1. 🌐 Universal Mailer Support

  • Custom SMTP: Any standard SMTP host with port flexibility (587, 465, 2525, 25), SSL / TLS / STARTTLS, and SMTP authentication.
  • Gmail / Google Workspace: Instant preset for Gmail SMTP with App Passwords.
  • Microsoft 365 / Outlook: Instant preset for Outlook enterprise servers.
  • SendGrid Web API v3: Direct HTTPS API (bypasses hosting port blocks completely).
  • Mailgun API: Supports both US (api.mailgun.net) and EU (api.eu.mailgun.net) regions.
  • Brevo (Sendinblue) API: Free tier friendly REST API.
  • Postmark API: Ultra-fast transactional email API with server token.
  • Resend API: Modern developer-first transactional email delivery.
  • Default PHP Mail: Automatic failover / fallback option.

2. 📋 Comprehensive Email Logger & 1-Click Resend

  • Keeps track of all outgoing emails with recipient address, subject, status (Sent / Failed), mailer used, date, headers, and attachments.
  • Modal Preview: Inspect the full HTML or Plain-text body of any past email.
  • 1-Click Resend: Re-deliver failed or previously sent emails directly from the dashboard.
  • Bulk Operations: Bulk delete and "Clear All Logs" options.
  • Auto-Cleanup Cron: Automatically prunes logs older than 7, 14, 30, 60, or 90 days to keep your database lean.
  • GDPR Privacy Mode: Option to turn off body logging for sensitive user data.

3. 🖥️ Live SMTP Handshake Terminal Debugger

  • Real-time terminal box showing the exact socket connection and SMTP dialogue:
    • EHLO identification
    • STARTTLS negotiation and cipher selection
    • AUTH LOGIN / verification
    • MAIL FROM and RCPT TO status
    • Server completion codes (250 2.0.0 OK)
  • Instant 1-click "Copy Log" button for easy support and debugging.

4. 🩺 Outbound Port Scanner & DNS Health Check

  • Port Scanner: Tests outgoing connections to ports 587 (TLS), 465 (SSL), 2525, and 25 to diagnose if your hosting firewall (e.g. GoDaddy, DigitalOcean, Hetzner, AWS) is blocking SMTP.
  • DNS Inspector: Checks if valid SPF and DMARC TXT records exist on your domain to prevent spoofing and ensure optimal deliverability.

5. 🛡️ Enterprise-Grade Security

  • All passwords and API keys are encrypted at rest using AES-256-CBC with keys derived from WordPress security salts (AUTH_KEY & SECURE_AUTH_KEY).
  • Complete nonce verification on all AJAX actions.
  • Strict capability checks (manage_options).
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🔄 How It Works (আর্কিটেকচার)

flowchart TD
    A["🛒 WordPress / WooCommerce / Forms / Plugins"] -->|Calls wp_mail()| B["⚡ Mail SMTP by Oi Interceptor"]

    B --> C{"Check Configured Mailer"}

    C -->|Custom SMTP / Gmail / Outlook| D["PHPMailer SMTP Handler"]
    C -->|SendGrid / Resend / Brevo / Postmark / Mailgun| E["Direct HTTPS REST API"]
    C -->|Default Fallback| F["Native Mail Dispatcher"]

    D -->|Real-time Socket Handshake| G["Outbound Mail Server"]
    E -->|Secure HTTPS Payload| H["Cloud API Gateway"]

    G --> I{"Send Success?"}
    H --> I

    I -->|Yes| J["🟢 Mark Sent & Write to DB Log"]
    I -->|No| K["🔴 Capture Error & Trigger Fallback"]
    K --> L["Save Error & Full Debug Trace in Log"]

    J --> M["📬 Recipient Inbox"]
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📁 Plugin File Structure

Mail SMTP by Oi/
├── mail-smtp-by-oi.php            # Main plugin header & bootstrap hook
├── uninstall.php                  # Clean database cleanup on uninstall
├── readme.txt                     # WordPress.org standard metadata
├── README.md                      # Comprehensive documentation
├── .gitignore                     # Git ignore rules
│
├── includes/
│   ├── class-oi-mail-smtp.php    # Singleton plugin bootstrap & lifecycle
│   ├── class-oi-options.php      # Settings management & validation
│   ├── class-oi-encryption.php   # AES-256-CBC credential encryption
│   ├── class-oi-mailer.php       # wp_mail dispatcher & hook interceptor
│   ├── class-oi-logger.php       # Database logger, resend engine & cron pruner
│   ├── class-oi-diagnostics.php  # Live port socket scanner & DNS checks
│   ├── class-oi-admin.php        # Admin UI, tabs, navigation & AJAX endpoints
│   │
│   └── providers/
│       ├── interface-oi-provider.php       # Standard provider interface
│       ├── class-oi-provider-smtp.php      # Custom SMTP, Gmail & Outlook driver
│       ├── class-oi-provider-sendgrid.php  # SendGrid v3 API driver
│       ├── class-oi-provider-mailgun.php   # Mailgun US/EU API driver
│       ├── class-oi-provider-brevo.php     # Brevo (Sendinblue) API driver
│       ├── class-oi-provider-postmark.php  # Postmark API driver
│       ├── class-oi-provider-resend.php    # Resend API driver
│       └── class-oi-provider-default.php   # Native fallback driver
│
└── assets/
    ├── css/
    │   └── admin.css                       # Responsive modern dashboard styling
    └── js/
        └── admin.js                        # AJAX form handler, test runner & modal
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🛠️ Installation & Quick Start (ইনস্টলেশন ও ব্যবহার)

১. ইনস্টলেশন:

  1. Mail SMTP by Oi ফোল্ডারটি আপনার ওয়ার্ডপ্রেসের wp-content/plugins/ ডিরেক্টরিতে আপলোড করুন অথবা অ্যাডমিন প্যানেল থেকে Plugins -> Add New -> Upload Plugin দিয়ে জিপ ফাইল আপলোড করুন।
  2. ওয়ার্ডপ্রেস ড্যাশবোর্ড থেকে Plugins মেনুতে যান এবং Mail SMTP by Oi প্লাগইনটি Activate করুন।

২. কনফিগারেশন:

  1. বাম পাশের অ্যাডমিন মেনু থেকে Mail SMTP-তে ক্লিক করুন।
  2. From Email এবং From Name ফিল্ড পূরণ করুন। (অন্যান্য প্লাগইন যেন ভুল ইমেইল দিয়ে না পাঠায় সেজন্য "Force From Email" চালু রাখা সুবিধাজনক)।
  3. আপনার পছন্দের মেইলার (Custom SMTP, Gmail, SendGrid, Resend ইত্যাদি) সিলেক্ট করুন।
  4. প্রয়োজনীয় ক্রেডেনশিয়াল প্রদান করে Save Settings বাটনে ক্লিক করুন।

৩. টেস্ট ইমেইল ভেরিফিকেশন:

  1. Send Test Email ট্যাবে যান।
  2. আপনার নিজস্ব একটি ইমেইল অ্যাড্রেস দিয়ে Send Test Email বাটনে ক্লিক করুন।
  3. লাইভ টার্মিনাল উইন্ডোতে হ্যান্ডশেক ডিবাগ লগ দেখে ডেলিভারি কনফার্ম করুন।
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🔑 Provider Configuration Guides

1. Google / Gmail & Google Workspace (Click to expand)

Google no longer allows less secure apps with normal passwords. You must use a Google App Password:

  1. Log into your Google Account and go to Security Settings.
  2. Ensure 2-Step Verification is turned ON.
  3. Under 2-Step Verification, scroll down to App Passwords.
  4. Create a new App Password (name it "WordPress SMTP").
  5. Copy the 16-character generated password.
  6. In Mail SMTP by Oi, select Google / Gmail:
    • SMTP Host: smtp.gmail.com
    • SMTP Port: 587
    • Encryption: TLS
    • SMTP Username: Your full Gmail / Google Workspace address
    • SMTP Password: The 16-character App Password (without spaces)
2. Microsoft 365 / Outlook (Click to expand)
  1. In Mail SMTP by Oi, select Outlook / Office 365:
    • SMTP Host: smtp.office365.com
    • SMTP Port: 587
    • Encryption: TLS
    • SMTP Username: Your Microsoft 365 / Outlook email address
    • SMTP Password: Your account password or App Password
3. SendGrid (Click to expand)
  1. Sign in to your SendGrid Dashboard.
  2. Navigate to Settings -> API Keys and click Create API Key.
  3. Choose Full Access or Restricted Access with "Mail Send" permission.
  4. Copy the API Key (starts with SG.).
  5. In Mail SMTP by Oi, select SendGrid and paste the key into the API Key field.
4. Brevo / Sendinblue (Click to expand)
  1. Sign in to Brevo.
  2. Click your account name at top right -> SMTP & API.
  3. Under the API Keys tab, click Generate a new API key.
  4. In Mail SMTP by Oi, select Brevo and paste the API key.
5. Resend (Click to expand)
  1. Sign in to Resend.com.
  2. Go to API Keys and click Create API Key.
  3. In Mail SMTP by Oi, select Resend and paste the API key (re_...).
6. Mailgun (Click to expand)
  1. Sign in to Mailgun.
  2. Go to Sending -> Domains and copy your sending domain (e.g. mg.yourdomain.com).
  3. Go to Settings -> API Keys and copy your Private API Key.
  4. In Mail SMTP by Oi, select Mailgun, enter your Domain, API Key, and select your Region (US or EU).
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🩺 Diagnostics & Outbound Port Scanner

Many budget or cloud web hosts block outgoing traffic on port 25, 465, or 587 by default. When this happens, PHPMailer hangs and displays timeout errors.

The Diagnostics tab in Mail SMTP by Oi includes an interactive port scanner:

  • Port 587: Standard TLS / STARTTLS submission port (Recommended).
  • Port 465: Traditional SSL submission port.
  • Port 2525: Modern alternative port supported by SendGrid, Mailgun, and major relays.
  • Port 25: Legacy unencrypted port (usually blocked by all cloud providers).

Clicking Run Port Test tests socket connections via fsockopen directly from your web server to your mail host, letting you instantly identify if hosting firewalls are the root cause.

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🔒 Security & Data Integrity

  • Encryption at Rest: Any passwords or API credentials stored in the wp_options table are encrypted with openssl_encrypt() using AES-256-CBC.
  • WordPress Salts Integration: Encryption keys are dynamically derived from your unique AUTH_KEY and SECURE_AUTH_KEY in wp-config.php.
  • Capability Guard: All administrative views and AJAX endpoints require the manage_options capability.
  • CSRF Protection: All settings updates, test sends, and log actions are strictly verified with WordPress security nonces.
  • Clean Uninstall: If the user checks "Completely delete all Mail SMTP by Oi settings and email logs when uninstalled", all database tables, options, and crons are cleanly removed upon plugin deletion.

❓ Frequently Asked Questions (FAQ)

ইমেইল কি WooCommerce এবং Contact Form 7 এর সাথে কাজ করবে? হ্যাঁ, 100% কাজ করবে। প্লাগইনটি ওয়ার্ডপ্রেসের কোর `wp_mail()` ফাংশনের সাথে ইন্টিগ্রেট করে। ফলে WooCommerce, Elementor Forms, Gravity Forms, WPForms, Fluent Forms কিংবা যেকোনো প্লাগইনের ইমেইল স্বয়ংক্রিয়ভাবে Mail SMTP by Oi দিয়ে যাবে। হোস্টিং যদি SMTP পোর্ট ব্লক করে রাখে তাহলে কী করব? আপনার হোস্টিং প্রোভাইডার যদি পোর্ট 587/465 ব্লক করে রাখে, আপনি **SendGrid**, **Brevo**, **Postmark**, বা **Resend** এর মতো **HTTP REST API** মেইলার ব্যবহার করতে পারেন। API মেইলারগুলো সাধারণ HTTPS (Port 443) দিয়ে কাজ করে, যা কোনো হোস্টিংয়েই ব্লক থাকে না। ইমেইল লগ কতদিন পর ডিলিট হবে? সেটিংসের **Log Retention Period** থেকে আপনি ৭, ১৪, ৩০, ৬০, ৯০ দিন নির্বাচন করতে পারেন অথবা আজীবন সংরক্ষণ করতে পারেন। ডিফল্টভাবে ৩০ দিন পর পুরোনো লগ স্বয়ংক্রিয়ভাবে মুছে যায়। ↑ back to top

🤝 Contributing

Contributions, issues, and feature requests are welcome! Feel free to check the issues page.

🏢 About Oi Technologies

Mail SMTP by Oi is proudly designed, developed, and maintained by Oi Technologies.

We build clean, robust, high-performance software and open-source tools for merchants, developers, and businesses across Bangladesh and worldwide.

Mail SMTP by Oi • Released under the GPLv3 License.
© 2026 Oi Technologies. All rights reserved.