False. Use a dedicated IP and don't send spam and you're fine (if you don't trust your users, run spamassassin in both directions). Google will complain about

False. Use a dedicated IP and don't send spam and you're fine (if you don't trust your users, run spamassassin in both directions). Google will complain about deliveries if you don't have IPv6 records. Everything else: DKIM, SPF, etc is optional and helpful. Simple greylisting works wonders to block incoming spam.