WP Mail SMTP

Another no frills SMTP plugin allowing you to configure proper SMTP mailing for your website forms receipts, notifications etc., increasing chances emails are delivered and not marks as spam. WP Mail SMTP has a very large user base and is well-supported, however, SMTP logging is a premium feature.

WP Mail SMTP screenshot

Extract from WordPress.org

Having problems with your WordPress site not sending emails? You’re not alone. Over 1 million websites use WP Mail SMTP to send their emails reliably. Our goal is to make email deliverability easy and reliable. We want to ensure your emails reach the inbox. WP Mail SMTP fixes your email deliverability by reconfiguring WordPress to use a proper SMTP provider when sending emails.

https://wordpress.org/plugins/wp-mail-smtp/