These are the best Recommend SMTP Extension for Magento Ecommerce.

I. Magento 2 SMTP Extensions:

1. Landofcoder SMTP Extension for Magento 2

This Magento 2 SMTP Extension for Magento 2 is created to choose to send reliable emails from a local hosting or custom server. Also, you can test your email easily with debug mode. And it allows you to log all sent email and view message in detail.

Link detail: https://landofcoder.com/magento-2-smtp-extension.html
Price: $126

2. MagePlaza - SMTP Extension for Magento 2

Free Magento 2 SMTP Extension improves your email reputation which is vital for every email marketing campaign. Say GOODBYE to SPAMBOX now! With friendly configurable port and host, brief modules along with user guide line stick below the fields, this extension is surely be useful for every online store.

Link detail: https://www.mageplaza.com/magento-2-smtp/
Price: FREE

3. Amasty Magento 2 SMTP Extension

- Prevent your emails from being labeled as spam
- Use reliable email providers to decrease email rejection
- View the content of sent emails
- Test your emails using debug mode
- Log all sent emails

Link detail: https://amasty.com/smtp-email-settings-for-magento-2.html
Price: $259

4. Xtento SMTP Extension for Magento 2 Ecommerce

Take full control over email sending settings in Magento 2! Easily configure your SMTP settings in Magento 2, including ready-to-use settings for more than 27 providers, as well as the ability to debug email delivery issues and make sure emails are sent properly using the extensions built-in email log.

Link detail: https://www.xtento.com/magento-extensions/custom-smtp-email-settings-for-magento2.html
Price: $129

5. Neklo Magento 2 SMTP Extension

Custom SMTP extension for Magento 2 allows sending emails with SMTP servers. With this extension you will get full control over Magento 2 SMTP configurations. This extension gives you the ability to change the default settings and send your emails with any custom SMTP server required, keeping your data secured.

Link detail: https://store.neklo.com/custom-smtp-extension-for-magento2.html

II. SMTP Extension for Magento Ecommerce

1. ASchroder.com SMTP Extension for Magento 2 Ecommerce

SMTP Pro is the best free, open source SMTP solution for Magento. It gives merchants complete control of custom SMTP server settings for sending magento emails and includes pre-configuration for popular services such as gmail and google apps.

Link detail: http://www.aschroder.com/product/smtppro-magento-smtp-email/
Price: FREE

2. MageCloud SMTP Extension for Magento

MageCloud partnered with ASchroder to offer SMTP Pro Email - Free Custom SMTP Email in your MageCloud panel for our simple 1-click installation option. To install this extension - create your account with MageCloud and launch a new Magento store. It takes only 3 minutes.

ASchroder always provides support for customers who have installed SMTP Pro Email - Free Custom SMTP Email Magento module. Feel free to leave a review for the company and the extension so we can offer you better products and services in the future.

Link detail: https://www.magecloud.net/marketplace/extension/smtp-pro-email-free-custom-smtp-email/
Price: FREE