Segment's emails can be scheduled. Then you will be able to send an email to a certain date time without going through campaigns.
- Create a segment first then add your contacts into this segment.
- Click on channels and emails and create a new segment email.
- Choose the segment and fill all mandatory fields on the right part of the email.
- After creating the email in the builder, publish it and choose a publish date (in the right part).
- This email will be sent the day of the publish date.
- Do not forget to add also an unpublish date otherwise emails will continue to be sent to new contacts that would be added to the segment.