I found emails in my Sent folder to a stranger, about meeting in San Francisco, ending in a random code. It wasn't a hack. It was warmup.
What warmup is
Tools like Instantly send AI-written emails between real inboxes in their network, all day, to build your sending reputation. Nobody reads them.
How to check
Search your email tool for the name. Zero hits in any campaign means it isn't your outreach.
Look at the ending. Warmup emails often end with a random string of letters and numbers.
Check the account settings. If warmup is on, that's your answer.
If none of that fits, treat it as a real problem: check your automations and change your password.
Should you turn it off?
On a new domain, keep it on. That's what it's for. I turned it off on my main inbox once it had a track record, and kept it on my 15 sending inboxes.