Spam Calendar Invites from my iCloud Address?

I believe I've figured this out. This is the well known Gcal spam, but in my case, at least, and I assume in yours, the Google calendar is linked to Calendar.app (formerly iCal) on your Mac. That means that an email alarm from Calendar when the Gcal spam is added sends an email from your primary email account using Apple Mail (or, more specifically, MailServiceAgent). No hacking. Just unfortunate behavior. It's also, fortunately, why it only goes to your own Gmail account.

See this article https://support.apple.com/kb/PH26234?locale=en_US

The spam calendar is viewed in gmail account because the gmail address and password is same as your Apple ID address and password , in system preferences > iCloud the Apple ID is signed in , and the web mail address is synced with iCloud server , so if a spam calendar invitation comes to iCloud .com ( Mac and iPhone are signed in with same Apple ID and password on the same network and synced ) and they will definitely shown in the devices .

While this may be just Gcal spam, don’t be sure that’s what ACPLE is referring to. A few of us have noted actual sent emails in our Sent folder from the sending account. See

https://discussions.apple.com/thread/250589495

See these help link https://support.google.com/mail/answer/81126?hl=en

https://support.google.com/mail/answer/6579?hl=en

Thanks, but not relevant to the situation I'm describing. What I'm talking about is messages actually being sent from my Exchange account --- the messages are actually in the Sent folder --- being accessed via Apple Mail.app on my work iMac.