Campaign's Daily Send Count

Each campaign has a daily send count, and this determines the number of mailings that will be sent each day once you activate your campaign. 
Once each day around midnight, Pebble will gather your active campaigns and send a batch of mailings according to the campaign's daily send count. Mailings will be sent in order according to the row number of your list file.
Mailers go out every day  at 2:00am UTC (7pm Pacific, 8pm Mountain, 9pm Central, and 10pm Eastern)

If you'd like to send an entire campaign in one day, simply set the campaign's daily send count to a really large number that is greater than the total number of properties of your mailing campaign.

To do this, click on Edit in your Campaign

Then change the number in the daily send count (in the example we've selected 1,000,000) and then click Save Campaign

Your campaign will then show the changes