What happens the moment a vault fires

The sequence

1. Your deadline passes. Nothing happens instantly; the scheduler runs on a cycle and picks the vault up within about five minutes.
2. The vault is claimed and marked as triggered before anything is sent, so a slow send can never turn into a duplicate send.
3. Attached files are fetched from encrypted storage and decrypted in memory.
4. One email is composed for each recipient: your message as the body, files small enough to send attached to it, and a private download link for anything too large to attach.
5. The email is handed to the delivery provider.
6. You are emailed to tell you the vault has been delivered, and the event is written to your audit log.

It only ever happens once

A delivered vault is finished. Its status becomes Delivered, the countdown stops, and it cannot send again. It stays visible in your account as a record. If you want the same thing set up again, copy the message into a new vault.

Large files

Email is a poor way to move large files, and every provider caps what it will accept. The delivery email carries up to around 9MB of attachments in total. Anything larger is not left out: it is delivered as a private download link in the same email, good for 90 days, which each recipient opens by confirming the address the vault was sent to.

So a folder of videos does reach the other end. It simply arrives as a download rather than an attachment, which is worth a sentence in your message so the recipient knows to follow it.

Can it be stopped?

Not after the fact. Once the email has left, it has left, and there is no recall. Before the fact it is entirely in your control: check in, pause the vault, lengthen the interval, or delete it.