Bulk email senders need to also stay clear of sending unwanted or unsolicited messages, provide one-click unsubscribe options, and reply to unsubscription requests inside two days. Failure to comply will lead to Gmail rejecting the offending emails. email. Though SMTP does most of the hefty lifting for email shipping, https://www.upwork.com/services/product/development-it-migration-to-magento-2-nodejs-in-new-vps-server-aws-linode-digitalocean-1445680653983371264?ref=project_share&tier=0