The reading-pane toolbar exposes a Done button (Shift+E). Done emails leave the inbox view but stay accessible under the Done tab. The key difference from Archive: when a new inbound reply lands on the thread, Done auto-flips back to undone and the thread returns to the inbox.

There are two ways to set one.

• While composing a new message: tick Remind me if no reply before you send, and the reminder is attached to the message as it goes out. The tick box is there for a brand-new message only, and only on accounts where the sent copy can be identified at send time. If you do not see it, send the message and set the reminder on it from the Sent view instead.
• From the message itself: open any email in the reading pane and click Remind me if no reply. This works on a message you already sent, and on one you received.

Either way you pick an interval from a short row of options (1, 3, 5, 7 and 14, plus your own default if it is not already one of them). Each option states its unit, so it reads 3 business days rather than a bare number you have to interpret. Once set, the control shows the date it will fire, for example Reminder set for Thu, Mar 5 if no reply, with a Cancel link beside it.

A reminder you set last week is easy to lose track of, because until it fires it lives on a message you may not open again. Open the Scheduled view in the inbox sidebar: above the queued sends, a Waiting on reply section counts and lists every reminder that has not fired yet, each with its subject and the day it is due. Click a row to open that message, or Cancel to drop the reminder without leaving the list. Once a reminder fires it leaves this list, and the section is hidden entirely when nothing is waiting.

Intervals are counted in business days unless you change it, so weekends are skipped rather than consumed: a 2-day reminder set on a Thursday lands on the following Monday, not on Saturday. The count runs in your workspace timezone, and the reminder is due at the start of the business day there.

To switch to plain calendar days, open Email settings (the gear in the inbox toolbar, or Settings > My preferences > Email inbox), and under Composing find Remind me if no reply. That one row holds both halves of the setting: the interval that is pre-selected for you, and the Business days or Calendar days switch beside it. The interval options name the unit you are on, so they read 3 business days or 3 days as you switch. Both are per user and follow you across devices.

Each morning a scheduled job checks the reminders that have come due and:

• If a reply has landed on the thread since you set the reminder, it is silently dismissed. You are not pinged about a conversation that already moved.
• Otherwise you get one in-app notification, titled Follow up: [subject], telling you the sender has not replied yet. Opening it takes you straight to the message.

The reminder is in-app only. It never sends you an email about an email. It fires once, and you can turn it off in Notification settings under Follow-up due.

To cancel a reminder before it fires, open the message and click Cancel next to the reminder line, or use the Cancel on its row under Waiting on reply. To push it out instead, cancel it and set a new one at a longer interval.

Once it has fired, the line on the message says so in the past tense, for example Reminder sent Thu, Mar 5, and the link beside it reads Dismiss rather than Cancel. Dismissing clears the line and frees the message to take a new reminder.