MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Voxbone - Fully compliant, enterprise-ready voice and SMS on demand. Build local presence on a global scale with elastic SIP trunks and phone numbers. Try for free.
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.
Twilio - Brings voice and messaging to your web and mobile applications.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.
Bandwidth - Bandwidth offers SIP trunking, Emergency communications, and Voice & Messaging APIs.