Mailjet is an email marketing software and API solution for teams, enabling them to design, deliver, and automate marketing and transactional emails.

SendPulse is a multi-channel marketing automation platform offering email, SMS, web push, and chatbots, designed to boost lead generation and customer retention for businesses.

UniOne is a transactional email service: you can send Transactional Emails simple and cheap with the help of platform API Email UniOne.

MTARGET is an all-in-one email marketing platform offering interactive emails, SMTP relay, and email validation to help businesses grow smarter with personalized cross-channel communication.

NotificationAPI is an all-in-one notification service for SaaS teams, offering email, SMS, push, and call delivery optimization with one API.

EmailsDesk appears to be a service related to email infrastructure, likely an email sending or delivery platform, given the domain name.

AotSend is a transactional email service API provider for developers.