Echo allows you to set up the message in advance and it will automatically be sent at your requested time. You can do this for either Simple or Bulk messages. Underneath the message section, there is a schedule message drop down.
Schedule message will let you pick a date and time to send the message.
Clicking in the Date field will present a calendar pop up which can easily be used to select the date of the send.
Then enter the time you want the message to be sent in 24h, so 23:05.
Check that the Timezone is correct, else your messages will be sent at a different time.
When ready simply click the Schedule messages button.
Editing / Cancelling Scheduled Messages
Scheduled messages can’t be edited once you’ve pressed the green ‘Send’ button, but they can be deleted by finding the message batch and clicking the red ‘Cancel’ button.
To help find the right batch, you need to find the message(s) in your Sent items and use the last updated time to find the batch.
You can cancel messages up to 5 minutes before they are scheduled to send.