Twilio - Brings voice and messaging to your web and mobile applications.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
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.
BulkSMS - SMS messaging service provider offering two-way SMS communication services.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.