Algolia - Algolia's Search API makes it easy to deliver a great search experience in your apps & websites. Algolia Search provides hosted full-text, numerical, faceted and geolocalized search.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Google Custom Search - Google Custom Search enables you to create a search engine for your website, your blog, or a collection of websites.
Brevo - Innovative online Email Marketing solution to manage your contacts, create & send your newsletters and track your results. More than 80 000 clients. Best prices and attractive features.
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.