SMTP clients and servers use textual commands and numerical codes to talk to each other. See the full list of them, as well as examples of SMTP sessions
Author: Zakhar Yung
SPF Records Explained
SPF record is a DNS record to protect your emails from being forged. Find out more about the Sender Policy Framework to increase the credibility of your product
Why Emails Going to Spam and How to Prevent It
Email spam filters are severe and can block even a refined email campaign. Learn how to pass through them and what you should do to reach the inbox.