Pay for Workspace, your spam won't be flagged as spam (by Google) and you get raised sending limits. Limits are based on licenses, so the more you pay Google, t

Pay for Workspace, your spam won't be flagged as spam (by Google) and you get raised sending limits. Limits are based on licenses, so the more you pay Google, the more you can spam, with a max of 4.6M unique addresses per 24H. If you send spam through Google, they will send your administrator an e-mail telling them that they are sending spam. If you send "a large volume" of this spam, they will stop relaying it until you promise not to send spam (or follow their guide to make your spam not look like spam).