Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
UseResponse - Open-source, self-hosted customer feedback software, live chat and helpdesk system that you can install on your server. Organize documentation using knowledge base and get feedback from social networks with centralized system
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.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.