Date rate limits define the minimum amount of time before a user will be sent a subsequent message in the Campaign series.
You can specify a date rate limit by hours, days, weeks or months by clicking the gear icon in your Campaign panel and inputting your preferences in the Settings screen:
If you set a date rate limit of 2 days and a user was sent the highest priority message, even if they immediately qualify for the next highest priority message, they will not be sent that message until 2 days after the first one was sent.
Date rate limiting is the final check when determining a user’s eligibility for a message. If a user meets the targeting criteria of (and is lined up to receive) a message, they will not be sent that message until this amount of time has passed since the last message they were sent. Once that amount of time has passed, all message targeting criteria is re-checked and only if a customer still qualifies for that message would they be sent the message.
Continuing with the example above, if a user triggers an event that disqualifies them from receiving a message that they were previously eligible to receive (but were not sent because they were date rate limited), they would not be sent that message after the date rate limit had passed because they would not meet the targeting criteria for the message when the messages in the series were re-evaluated.
Regular Messages vs Campaign Date Rate Limiting
Regular messages (that are not in Campaign) won't interfere with the ‘Rate limiting’ of your Campaigns. Users who received a regular or one-off message will still be eligible to receive Campaigns according to the selected ‘Rate limit’ defined in Campaigns. This means you can schedule and send regular messages to your users without worrying if it will delay your Campaigns from sending.
As an example, you might have a Campaign with a rate limit of "at least 1 day apart" and decide to send your users a one-off message. In this scenario, users who qualified for the Campaign on the same day as the one-off message would receive both those messages that day.