Learn how to build an email loyalty program with better rewards, stronger retention, and more relevant customer engagement through email.
Author: Pankaj Kumar
Pankaj Kumar
Pankaj Kumar is an Email Deliverability Expert and Product Leader with 13 years of experience in email deliverability, CRM, marketing analytics, deliverability onboarding, implementation, and automation. He combines deep technical expertise in email infrastructure, inbox placement, sender reputation, and authentication protocols with a product-driven approach to solving complex deliverability challenges at scale. Having worked with Zeta and Blueshift, Pankaj has helped hundreds of clients improve email performance through data-driven strategies, technical troubleshooting, and scalable automation. His focus extends beyond resolving deliverability issues to building smarter deliverability products, monitoring systems, and AI-powered solutions that help businesses proactively identify risks and improve inbox placement. Through his blog at University of Email, Pankaj shares practical insights on email deliverability, CRM strategy, marketing analytics, and emerging deliverability technologies to help email marketers and technical professionals make informed decisions and achieve better results. Connect with him on LinkedIn at https://www.linkedin.com/in/pankajkumar-deliverability
Learn what a CDP is, how to evaluate a real customer data platform, and which checklist items matter most for modern marketing teams.
No matter, if you’re running a start-up or you’ve established business – you’ll need help of ESP to keep communicating with your subscribers via Email. In this article we’re going to bring some key question while selecting a basic ESP. There are more than hundreds of ESPs in the market – you’ll need to choose those who fits you best. Luckily, you don’t need a sixth sense to choose the right ESP. Follow this checklist of questions when interviewing potential ESP partners to find the right fit. There are some categories and you can brain storm yourself around that. See below…
Unfortunately, there is an another incident of data breach. This time Twilio which has disclosed that attackers tricked an employee into sharing their credentials. Meaning allowing them to access information for a “limited number” of customers. A ‘sophisticated’ SMS phishing attack on Twilio employees allowed hackers to access some customer data. The company said it has been notifying affected customers individually. “If you are not contacted by Twilio, then it means we have no evidence that your account was impacted by this attack,” the company said. The company did not disclose how many customers were affected or what types of…
Learn how to maintain a clean email list with practical list hygiene steps that improve deliverability, reduce bounces, and protect sender reputation.
4.7.8 Email Bounce Error Reason User Authentication Failed: Delayed Message The email message has not yet been delivered because the sender’s email program did not provide your correct username and password to the sender’s email system, which requires these to prove your identity. How to fix? In the sender’s email program’s account settings, look for “SMTP” (which is about sending email) and, in the SMTP area, “authentication”. Ensure that the username and password are entered correctly there. If this error persists, contact the email provider for help. 4.7.8- Official definition from ITEF For the code that starts from 4.X.X A…
4.7.7 Email Bounce Error Reason Potentially Corrupt Message: Delayed Message The email message has not yet been delivered because an email server involved with sending the message had difficulty processing the security features of the message. The message was possibly corrupt or altered in some way during sending. How to fix? If intentionally sending ecrypted email messages, check the sender’s email program settings and make necessary changes. Retry the email message see if the same error occurs, or if it was a one time problem. Otherwise, contact the sender’s email support team or encryption provider to help identify any misconfiguration…
4.7.6 Email Bounce Error Reason Message Encryption Issues: Delayed Message The email message has not yet been delivered because an email server involved with sending the message had difficulty processing the security features of the message. How to fix? If intentionally sending ecrypted email messages, check the sender’s email program settings and make necessary changes. Retry the email message see if the same error occurs, or if it was a one time problem. Otherwise, contact the sender’s email support team or encryption provider to help identify any misconfiguration with the sender’s account or encryption tools. 4.7.6- Official definition from ITEF…
4.7.5 Email Bounce Error Reason Message Authentication Issues: Delayed Message The email message has not yet been delivered because your email sending system uses DKIM, an authentication mechanism. Either the sending or receiving email system had some problem with the sending system’s DKIM. How to fix? Check if it is one time issues – retry sending message again after few hours. If problem persists you may need to dig out further to make sure it doesn’t have DKIM issues. If the problem continues, contact the sender’s email support team to help identify any misconfiguration with the sender’s account or with…
4.7.4 Email Bounce Error Reason User Authentication For Message Failed: Delayed Message The email message has not yet been delivered because there was a problem with your user authentication to your email system How to fix? Review the email account settings. Check for options that require “user authentication” for outbound SMTP and ensure that the Username and Password values are correct. If the account settings are correct, contact the email provider to help identify any misconfiguration with the sender’s account or with the email system. 4.7.4- Official definition from ITEF For the code that starts from 4.X.X A persistent transient…