How does Engage deal with retrying a Send within a journey?

Imagine a Journey where you do an Email Send, and want to retry sending to contacts who were excluded in previous steps.

In the example below, we would try to do a Send on day 1, send to contacts who are included, and wait 2 days for contacts that are excluded.
On day 3, contacts are re-evaluated. Contacts that are included receive the email, for contacts that are excluded we wait 2 days.

On day 5, contacts are re-evaluated. Contacts that are included receive the email, contacts that are excluded exit the journey.

This way, contacts receive the Send as soon they can receive it without hitting the limits defined in the rules. If a contact is oversaturated, they will be excluded from a Send, but they can be re-evaluated 2 days later.

In this configuration, all DESelect Engage components in the journey have the same Send selected. On the campaign calendar, the Send would be configured with the Planned Send Date of the first sending.

When a contact hits the first DESelect Engage component, the sending happens at the moment DESelect Engage expected it, so Engage will provide the Include/Exclude outcomes as expected in the preview.

When a contact hits the second DESelect Engage component, the sending happens 2 days after the Planned Send Date for the campaign. This is not a problem though; for 3 days after the Planned Send Date, DESelect will continue to expect the Send to happen that day, and the contact will be Included as long as slots are available. This means that in the daily calculations, this Send will be taken into account together with other Sends that are in scope for each contact.

When a contact hits the third DESelect Engage component, the sending happens 4 days after the Planned Send Date for the campaign. In this case, DESelect Engage is no longer including this Send into its daily calculations, and the Send is considered an unplanned Send. The evaluation of the outcome will happen the moment the contact hits Journey Builder. The outcome will be Included if:

- there are slots readily available after the last daily calculations

- or if this Send has a higher priority than Sends for which a slot was reserved. In that case, the Send with the lower priority is switched out for the unplanned Send.