When you send emails in Engage, a series of events and processes take place behind the scenes before your email reaches a subscriber's inbox. Usually this happens in a matter of seconds, but sometimes, depending on the size and complexity of the send, it can take minutes or in extreme cases, hours for delivery to all subscribers.
This article briefly describes the Engage sending process. Though you can't control behavior of the system at this level, understanding what occurs may help you evaluate why your send executes immediately or takes longer than expected.
Step 1: You click Send
The first step in the process occurs when you click Send or when the Engage system picks up a send that was previously schedule to execute. When this happens, the Send enters a Queued status and becomes available for the Engage task servers to pick up and begin processing.
Step 2: Engage begins processing the job
Once an Engage task server begins processing the send job, the status will change to In Process. At this point, the system is actively assembling your messages.
Step 3: Engage pulls the list of subscribers
Engage begins by pulling the appropriate subscribers for the send. This includes all active and subscribed customers who are a match for your segment or are members of the targeted List. Subscribers who have been suppressed due to bounce management or invalid addresses are automatically excluded.
Step 4: Engage builds the messages
Next, Engage begins building individual messages for each subscriber in your list or segment. If the send contains dynamic content or personalization logic, that scripting is replaced with actual content and subscriber data within each message. Unique view as web page and unsubscribe links are generated for each subscriber’s email.
Step 5: Engage batches and begins sending the emails
As emails are assembled, they are bundled into batches of 5000 and transmitted by a network of Engage mail servers to each recipient mail server. When the final message has been packaged and handed off for delivery by the mail servers, the send job is marked as Sent.
This entire process can be very intensive. If your send is complicated with complex content or contains millions of subscribers, it may experience delays before arriving in all of your customers' inboxes.