Publish your domain’s DMARC document to avoid phishing and spoofing. If you’re using a shared IP account from the supplier like SendGrid, don’t setup DKIM and DMARC. It forces your mail streams to have “domain alignment” that can result in your emails to fall short authentication and start bouncing. https://gunneroepbl.blogrelation.com/32680073/server-security-expert-no-further-a-mystery