250ok VS rapidmail

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.

Mailjet - All-in-one email service provider that provides maximum insight and deliverability results for both marketing and transactional emails.

Litmus - litmus tests and tracks your email campaigns, so you can always put your best design forward.

Mailgun - A set of powerful APIs that enable you to send, receive and track email from your app effortlessly whether you use Python, Ruby, PHP, C#, Node.js or Java.

Return Path - Inbox placement solutions from Return Path helps improve email deliverability and increases email marketing ROI.

PHPMailer - Email sending library for PHP.