What AI chat can and can't do
AI chat has a per-day limit that resets every day: 20 on Free and Plus, 100 on Pro, and 400 on Ultra. Chat doesn't use credits, only the daily cap. Draft replies have their own separate daily limit. If you hit the cap, chat picks back up the next day.
The daily chat limit
AI chat is capped by how many messages you can send per day, and the cap depends on your plan. It resets each day, so a fresh allowance is waiting the next morning.
Chat doesn't use credits
This is the part people most often get wrong, so to be clear: asking the AI chat a question does not spend any credits. The only thing credits ever pay for is processing your incoming email, roughly one credit per email read and sorted. Chat is limited purely by the daily cap above. See How credits work for the credit side of things.
Draft replies have their own limit
Draft replies are counted separately from chat. They have their own daily cap (6 on Free, 10 on Plus, 30 on Pro, 100 on Ultra) and, like chat, they do not use credits. So sending a bunch of draft replies does not eat into your chat allowance, and vice versa. More on that in Generate an AI draft reply.
When you hit the cap
If you reach your daily chat limit, chat pauses for the rest of the day and comes back with a full allowance the next day. Everything else keeps running in the meantime: your email is still being processed, your briefings still arrive, and your Action Items, Highlights, and FYIs are all still there. If you regularly run out, a higher plan raises the cap.