Send-once
Send-once is a rule that makes an automation send each message exactly once, however many times someone presses approve or the same event arrives. It's how you prevent duplicate emails. Without it, a double tap, a slow screen or a retry can put the same reply in front of a lead twice.
Why it matters
A duplicate reply is the kind of mistake a lead notices. Two identical emails a few seconds apart make a business look careless, and it happens right when someone has decided to get in touch. The causes are ordinary: a button pressed twice, a screen that didn't respond so someone pressed again, or a tool that retried a step after a timeout. None of that is unusual, so the protection has to be part of the system from the start.
An example
As an example, an account lead at a small agency gets a drafted reply on their phone between meetings. They press approve, the screen doesn't change, so they press it three more times on the way into the next call. Without a send-once rule, the lead on the other end gets four copies of the same email, and the first impression is a business that can't work its own tools.
How a system handles it
Before it sends anything, the system writes down that this message is being sent, and every press checks that note first. The first approval claims the message, and every later press finds it already claimed and does nothing. On an inquiry desk I built, running on SignalNine's own inbox, five approve presses landed in 2.2 seconds on 2026-09-07, and it sent one email.
Questions
Can't I tell people to press approve once?
You can, and someone will still press twice on a slow connection. Tools also retry steps on their own after a timeout, with nobody pressing anything. The rule has to live in the system, because some duplicates come from places a person never sees.
What do developers call send-once?
Idempotency: doing the same thing twice has the same effect as doing it once. In owner terms, one approval means one email, whatever happens around it.
Related
- Human-in-the-loop approvalWhat human-in-the-loop approval means in an automation, which steps should wait for a person, and how an approval card makes sure an email sends once.
- How do I approve email replies from Slack before they go out?Approving email replies from Slack, Telegram or Google Chat: what the built-in apps do, where an approval loop breaks, the send-once rule, and what I'd pick.
- What a reliable automation looks likeFive properties any automation should have, checkable by an owner who doesn't build: logged runs, named alerts, one send per approval, safe reruns, an owner.
- A drafted reply to each lead, approved from my phone before it sendsAI drafts replies to lead emails that pass a junk screen, from my business facts. Risky asks get flagged, and nothing sends until I approve it on my phone.