OpenSlot for Outlook

OpenSlot is an Outlook add-in and web app for scheduling meetings by email. Pick the people, a date window and a timezone; OpenSlot checks their Microsoft 365 free/busy and returns one clean list of every time slot when everyone is free, grouped by day and ready to paste. In Outlook, the list is inserted straight into the email you are writing, and on a received email "Reply with times" opens a reply-all with your availability already in it. Unlike booking-page tools, there is no link for the other person to click: they just reply with a time.

Features:

• Merges availability for up to 40 people (Pro)
• Any timezone, 1 to 60 days ahead, custom working hours, weekends on or off
• Shortest slot from 15 to 60 minutes; tentative meetings can count as busy
• "Just me" mode for sharing your own free times
• Works in Outlook on the web, Windows, Mac and the new Outlook, plus a web app
• Read-only free/busy only: never reads meeting titles and stores no calendar data; no admin consent needed

Pricing: every account starts with a 14-day Pro trial (no card), then a free plan for you plus one person with a 7-day window. Pro is $7 per user per month; Team plans start at $5 per user per month.