This is worrying. I received a message from Fastmail saying I had reached my sending limit for the day. Impossible. I raised a ticket and 8.5 hours later got confirmation my account had been compromised. I'll say this for Fastmail; the recovery process is superb. The worrying part is that I know I did not reply to any phishing expedition. So how did it happen? Brute force, maybe. Pwned, maybe.