Google Apps is spamming from my domain. What could be?

Question

Google Workspace

There is mail in Google Apps (free account). Spam letters began to arrive, as if they were sent to themselves, i.e. from [email protected] to [email protected] And what is most incomprehensible - in the [email protected] account, these letters are in the sent folder. Passwords have been changed, we do not use mail clients, forwarding and work with mail clients are disabled in the settings, mac computers. How is this even possible and what should be done? I really don't understand what it is and how it's possible.

Answer 1

Look for a Trojan/keylogger/etc on the PC/smartphone where the box is being used.