How can I overrule saturation control to make sure a certain campaign is sent?

To make sure a campaign is sent, no matter the saturation levels of contacts, saturation control can be disabled for a campaign.

To do this:

• Inside DESelect Engage, from the Campaign calendar, on both the Calendar View and List View, you can click on Exclude Campaign. This allows you to select the campaign(s) that you want to exclude. Once a campaign is excluded, it will show up on the Excluded Campaigns section on the list view. Campaigns in this section are excluded from saturation control. DESelect Engage will not apply any logic and let all sends through, and ignore these sends in future saturation control decisions.
  
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• Inside Journey Builder, on the DESelect Engage journey builder component, there is a switch called 'Saturation Control enabled'. For campaigns that have been marked as excluded in Engage, this switch will be turned off already. If you turn off the switch in Journey Builder for that campaign, the campaign will be shown as excluded inside Engage.

Note: alternatively, you could also not add the Engage journey builder component to your journey. Note that in that case the send will still be considered as the data views are ingested. DESelect Engage will take this send into consideration in a contact's history and it will impact the contact's saturation levels.
For example: if you sent an email through Journey Builder without the DESelect Engage component, the send will still be ingested by Engage. While the system does not know the campaign type in that case, it does know the channel, so this will count against rules like 'max. 3 emails per 7 days'.

In contrast, when you add the Engage component but turn off 'Saturation Control enabled', this send will be ignored completely. Engage will send all contacts through the Undersaturated branch, and the send will also not be ingested, so it will not count toward contacts' saturation levels and rules.