You can choose what time an email will be sent using the Schedule Email function.
Simply compose your email like normal. Then, next to your Send button, you have an option to choose a scheduled time. A selection of common options will be provided, or you can also choose a custom day and time.
If you need to make an edit to your email prior to sending just cancel the send, edit the email and set up the schedule again.
Step 1: Navigate to the Main Menu of your account
Step 2: Click on 'Triage', you'll see a second menu appear showing options to choose from.
Step 3: Choose 'Scheduled' and find the email that you would like to edit.
Step 4: In the scheduled email you'll see the option to 'Cancel Send', click on that link, edit your email and re-schedule your email.