How do I use AI to summarize long email threads
Paste the thread into an AI chat tool like ChatGPT or Claude and ask it to summarize the decisions, open questions, and action items with owners. For recurring use, turn on your inbox's built-in AI summary — Gmail's Gemini side panel and Outlook Copilot both summarize a thread in place without any copy-paste.
The prompt matters more than the tool. "Summarize this" gets you a shorter version of the same confusion. Ask for structure instead: "List the decisions made, the questions still open, and every action item with who owns it and when it's due. Flag anything where two people disagreed." That last instruction is the one people skip, and it's the one that saves you — buried disagreement is the whole reason long threads become expensive. For the copy-paste route, open the thread, expand all the collapsed replies (this is the step people forget — collapsed quoted text often doesn't copy), select everything, and paste it in. Twenty-message threads are fine. If you're working with something enormous, split it in half and summarize each part, then ask the tool to merge the two summaries into one timeline. Built-in options skip the copy-paste entirely. In Gmail, the Gemini side panel offers a "Summarize this email" button on long threads if you're on a Workspace plan that includes it. Outlook's Copilot does the same thing and will also draft a reply based on the thread. Both are faster for daily triage; a standalone chat tool is better when you need a specific analytical angle, like extracting every commitment made to a client across six weeks of back-and-forth. One caution worth taking seriously: don't paste threads containing client contracts, salary details, medical information, or anything covered by an NDA into a free consumer AI account. Free tiers may use your input for model training. Paid business tiers — ChatGPT Team, Claude for Work, Microsoft 365 Copilot, Gemini for Workspace — contractually exclude your data from training. If the thread would make you nervous in a screenshot, use a business account or don't use AI on it at all.