- ActiveCampaign – https://www.activecampaign.com – best according to Alicia St. Rose (South Central Coast WordPress Adventure Group)
- Postmark App – https://postmarkapp.com (integrates with ActiveCampaign)
- ConvertKit – https://convertkit.com
- MailPoet – https://www.mailpoet.com/
- WordPress based newletters marketing
- owned by WordPress/WooCommerce
- MailerLite – https://www.mailerlite.com
- MailChimp – https://mailchimp.com
- Featured Images in RSS for Mailchimp & Other Email –
https://wordpress.org/plugins/featured-images-for-rss-feeds/
- Fluent SMTP Plugin – https://wordpress.org/plugins/fluent-smtp
- SendGrid – https://sendgrid.com