Critsend is a SMTP relay. The service is simple to implement . We go further than our competitors by giving you a clear vision on your deliverability rate. We track your sendings and provide you with solutions to eventual deliverability issues. We go from large campaigns to newsletters, and transactional emails. We refuse spams, and they are monitored by our tools. We tolerate up to 10Mo per email. Our servers are made to keep persistent connexion. We give you the possibility to add any header starting by X-***. We process encoding along with your campaigns.