Plain Gmail and plain Outlook have no built-in way to show that a colleague is drafting a reply. You need either a shared inbox tool with collision detection, meaning a typing indicator on the thread, or a manual claiming convention. Tool-based detection is the version that holds up, because it does not depend on anyone remembering to do anything first.
It happens in the first hour of the morning. A client writes in with a question. Two people open it at roughly the same time, both think nobody else has picked it up, and both reply. The client gets two answers four minutes apart, and if the answers do not match, they now have a question about your team.
Everyone who has run a shared mailbox has done this. It is not a discipline problem. Plain Gmail and plain Outlook give you no way to see that a colleague is in the same thread right now. The only defense is talking to each other, which stops working past a handful of people or across a single time zone.
Is there a Gmail add-on that shows when someone else is replying?
Yes, several, though what they show varies more than the marketing suggests. Gmail itself has nothing for this. Google Groups collaborative inboxes let you assign a conversation, but assignment is an act after the fact and says nothing about who is typing now. Outlook shared mailboxes are the same: everyone sees the thread, nobody sees the draft. So the answer is always an add-on or a separate tool.
The versions you will find fall into three groups, and you should know which one you are buying.
- Presence indicators show an avatar or a small label on the thread when a teammate has it open. This is the lightest version and the commonest.
- Draft-level warnings detect that someone has started typing a reply, and warn anyone else who tries to do the same. This is the one people mean when they ask for it.
- Locking and assignment give the thread a single owner. Others can read it, and replying requires owning it first. The strictest option, and the one support teams lean toward.
Presence alone is weaker than it sounds. Someone can have a thread open in a background tab for twenty minutes without touching it, which trains the team to ignore the indicator. If double replies are a real cost for you, ask the vendor whether the signal fires on opening or on typing.
Which shared inbox tools have collision detection?
Each of the common tools has some form of it. The table covers where the feature sits in each product, based on public documentation checked in September 2026. Behavior changes between tiers, so confirm on your plan.
| Tool | What it shows | Where your team sees it |
|---|---|---|
| Sektra | A typing indicator on the thread that reads A teammate is typing a reply, plus assignment so each thread has an owner | In Sektra, synced two-way with Gmail, Outlook and WhatsApp |
| Front | Presence and draft indicators, plus assignment | In the Front app only |
| Hiver | Collision alerts and assignment status | In the Gmail interface |
| Missive | Presence and shared drafts | In the Missive app only |
| Help Scout | Viewing and typing indicators on a conversation | In the Help Scout app only |
| Gmelius | Presence on shared labels and assigned conversations | In the Gmail interface |
| Google Groups | None. Assignment only, after the fact | In the Groups web interface |
The third column is the one people underweight. If half your team works in Gmail or Outlook and the tool shows the signal only in its own app, the likeliest colliders never see the warning. That is the practical argument for a tool that syncs with the mailbox two ways, which is how we build Sektra. The indicator shows in Sektra, and a reply sent from Gmail or Outlook syncs back into the thread. The second person sees it was answered before they send.
How do you stop double replies without buying a tool?
You can get part of the way with a convention, provided the team is small and works overlapping hours. Three that work in practice.
- Claim in a channel. One Slack or Teams channel where you post the subject line before you start typing. Crude, and it works for a team of four. It stops working the moment someone is heads down and forgets.
- Label as a lock. In Gmail, a shared label such as handling followed by your name, applied before you reply and removed when sent. In Outlook, a category does the same job. Visible to everyone in the mailbox, and requiring no extra tool. It depends on people applying it first, which is the moment they are least likely to.
- Rota by hour. One named person owns the inbox for a block of the day and is the only one who replies. Everyone else can read. The most reliable manual option, and the least popular, because it makes one person responsible for a queue they did not choose.
Every one of these fails the same way. It depends on a person doing something before they do the thing they want to do, which is answer the client. That is why teams that grow past a handful of people end up buying something.
Why assignment on its own does not solve it
Teams buy a shared inbox, turn on assignment rules, and assume the problem is handled. Often it is not, and the reason matters. Assignment answers the question of who should deal with this thread. Collision detection answers the question of who is dealing with it right now. Only the second one prevents the client from getting two replies.
The gap shows up on threads that arrive before the rules run, on threads reassigned mid-conversation, and on the account everybody feels ownership over. A large client writes in, three people who all work with that client see it, and each thinks their answer is the one needed. Assignment does not stop that. A live typing indicator does.
What good collision handling looks like in practice
If you are evaluating tools, these are the behaviors to test during a trial.
- The signal fires when someone starts typing, and does not wait for a reply to be sent.
- It is visible without hovering or clicking. It should be in your peripheral vision from the list view.
- It clears itself. Indicators that get stuck because someone closed a laptop lid teach people to ignore them.
- It works across devices, so a colleague drafting on a phone is visible to someone on a desktop.
- It survives reassignment, so handing a thread over does not leave two people thinking they own it.
One more that gets missed: the thread where the reply is not the whole story. If your team's answer depends on what somebody promised the client last month, the collision you want to avoid is two different answers. Two replies is only the visible symptom. A per-client record of commitments and open questions lets the second person see what the first one would have said. That record is what relationship memory is. The same problem gets worse across time zones, where the first person is asleep.
A short rollout that sticks
Turning the feature on is not the same as changing the behavior. Four steps that take about a week.
- Count the problem first. Search sent mail for the last month and find threads with two replies from your side within ten minutes. Having the number makes the case for you.
- Turn detection on for everyone at once. A partial rollout means half the team is invisible to the other half, which is worse than nothing.
- Agree one rule out loud. If you see the indicator, you do not reply, you comment internally. The rule matters more than the feature.
- Recount after two weeks. If the number has not moved, the signal is firing too late, and that is a vendor question.
The reason this deserves a week of attention goes beyond embarrassment. A client who receives two different answers from your team stops trusting the first answer they get from you, and that cost keeps accruing long after the thread is closed. Customer success and account teams, whose clients write to several people at once, have the most to lose from it.
