You can set the cutoff time for campaigns across all accounts in your organization using Settings > Messaging settings > Campaigns > Cutoff time page to prevent your user's campaign messages from being sent after the selected time. Messages that miss the cutoff time are moved to the Skipped folder on the dashboard of the Campaigns page.
Note: This setting is available to org admins only. You can configure this setting for all accounts in your organization by logging in as an org admin and configuring this setting on your organization account.
Note that campaign messages that are not sent due to the cutoff time will not count towards your daily campaign message limit.
