Comment by IncandescentGas

This is not always the case.

Last week, my monitoring system sent me 20k emails in a few hours in response to a server attack.

When those hit my gmail inbox, gmail marked them all as spam. Myself, the user, did not mark them as spam. Gmail did that for me. But their reputation system is behaving as if 20k people marked 20k emails from us as spam.

In response to those 20k emails marked as spam, now our domain sender reputation with gmail is LOW, and our low volume of legitimate email with customers goes to their spam folders.

The gmail client gives me no way to unmark these messages as spam, except to click on each message, one at a time, and dig into a submenu to find the "Not spam" button.