If your organisation uses Docmail as its output channel, be aware that submitting a job to Docbox is not the same as it being despatched. Your job goes through several processing steps first, queueing, validation, and batching, and how long this takes can vary depending on how busy the system is at that moment.
Docmail also applies its own daily cutoff for next-day despatch. If you need a job to go out today, submit it well ahead of that cutoff rather than close to it, since there is no way to guarantee exactly how long Docbox's internal processing will take.
You can check a job's current status on the dashboard at any time. If you're unsure whether it will make today's despatch, contact your Docbox administrator.
See also: Docmail's delivery schedule.