Deliverability Engine

Cloud Distributed Architecture

Availability & Reliability

We have many servers distributed on several continents. Fault tolerance is built into our array of independent servers. For instance, when a server in the CritSend's Deliverability Engine Cluster sends a message, it is replicated on several other machines. Our cluster has a 99.99% availability and very high reliability.

Scalability

CritSend easily scales for your success. Our Deliverability Engine's design ensures scalability, and active real time load balancing that truly adapts to your changing daily traffic needs; your mail is quickly delivered reliably. If you have a massive-recipient newsletter to send one day or experience a suddenly large increase in transactional social networking messaging, our Deliverability Engine can handle it without affecting delivery speed.

Reputation Management

Spam Filtering & Alerts

CritSend's Deliverability Engine makes sure that legitimate emails land in their appropriate recipient inboxes. We analyze and repackage each email optimizing it with legal and technical compliance additions, and filter it for spam and bounces. The Deliverability Engine analyses each email for spam before it is sent to its destination ISP. This prevents customers from unwittingly sending emails that will be blocked by ISPs and is especially useful for transactional emails on social networking sites where spammers try to exploit site messaging. Spam alerts are sent to our customer so they can rework the potentially offending mail and send it again, without damaging their reputation. Some messages that have good content such as are seen by some ISPs as spam nonetheless for various reasons, and we check messages against multiple filters. We only stop these problematic emails, allowing your other mail to pass through. Most importantly, you are automatically notified of deliverability issues in real time. Never again worry about the state of your transactional messages, password notifications or invoices.

Continuous Testing

Each server tests itself regularly for deliverability using technologies such as real-time blacklist detection, log analysis among others. When a server encounters an issue with a specific ISP or blacklist, it automatically rebalances its affected load to other servers and alerts are sent to CritSend HQ for immediate investigation. This ensures that there is no disruption in customer mail streams. See our complete feature list.

Deliverability Management

Built-In Compliance & Authentication Features

CritSend's Deliverability Engine takes care of CAN SPAM compliance for you and appends your emails with specific CAN SPAM content footers, DomainKeys signatures and SPF/SenderID. We also handle all aspects of unsubscription management for you including automatically appending your unsubscription message to your emails and full unsubscription request processing. We store unsubscription addresses, bounces and spam report clicks. Their addresses are filtered from your deliveries, and you may edit them through the website dashboard or export them in real time through an API query.

Advanced Delivery Management Features

CritSend employs feedback loops with major ISPs allowing you visibility into custom insights such as who pressed the "report spam" button on your mail. Our smart bounce processor is fine-tuned to each ISP. We are able to differentiate soft bounces such as temporary bounces from hard bounces such as invalid addresses. CritSend's Deliverability Engine retries soft bounces.

And as major ISPs have different receiving preferences such as maximum connections, allowed retry attempts per hour, preferred authentication methods, and others, the Engine optimizes for each recipient ISP's policies and stays abreast of changes. Learn about our other delivery management features here.