SMTP Connection Encryption: The Key to Secure & Reliable Email Delivery
One of the top channels of communication for businesses is email, which unfortunately makes it one of the prime targets of cyberthreats like phishing, data interception, and spoofing. Encryption is the answer. Without it, emails are transmitted as plaintext over the Internet where people can steal sensitive information. SMTP (Simple Mail Transfer Protocol) is the […]
SMTP Error 421 4.4.1 – How to Fix It [SOLVED]
![Text on a white background reads: SMTP Error 421 4.4.1 How to Fix It [SOLVED], with smtp error 421 4.4.1 and How to Fix It [SOLVED] highlighted in red.](https://warmy-blog-wordpress-bucket.s3.amazonaws.com/wp-content/uploads/2025/02/09012311/SMTP-421-441.webp "SMTP Error 421 4.4.1 – How to Fix It [SOLVED] 3")
This guide goes through how to resolve SMTP Error 421 4.4.1 – No Answer from Host error and prevent it from occurring again with best practices.
SMTP Retries and Deferrals: Understanding Email Delays & How to Fix Them
The main protocol for sending email is the Simple Mail Transfer Protocol (SMTP), which manages both the sending and routing of messages between networked devices. But the journey from sender to recipient can sometimes be rocky. This may also result in SMTP retries/deferred by the senders. Though these mechanisms are supposed to be able to deal with […]
Fixing Reverse DNS Lookup Failures Best Practices for Email Server Configuration
Email is an instrumental communication tool that finds its advantages in areas such as marketing, customer support, and other internal communication processes. Email marketing is considered as the “king of all marketing channels”, while email communication for both customer support and internal communication offers a non-time sensitive system allowing everyone without rushing too much of […]
SMTP AUTH Mechanisms Explained Choosing the Right Authentication for Secure Email Sending
Phishing attacks, and spam emails remain a continuous problem for many email users. One of the most notorious forms of email security issue is the unauthorized access or usage of a bad actor or a spammer towards an email. If this ever happened to you then that means that you probably have an issue with […]
Reverse DNS Lookup Failures How They Impact Email Deliverability and Sender Trust
Email is a valuable communication channel, especially for many businesses and email marketers. It is known to develop the highest ROI, which should make inbox placement and email deliverability a priority. The capability to ensure that your emails are delivered to the intended recipient is a simple idea, yet there are still some email users […]
Why SSL & TLS Certificate Errors Are Hurting Your Email Deliverability
If you are an email marketer, you probably understand that having the best email and domain setup are one of the fundamentals to ensure that you have a functioning email. However, one factor that can still affect your email deliverability and overall reputation are errors caused by SSL (Secure Sockets Layer) and TLS (Transport Layer […]
Maximizing Email Deliverability: Grouped vs. Randomized Sending
Many organizations suffer the pain of emails ending up in spam folders or being throttled—often because sending practices are widely inconsistent with Outlook 365’s spam filters. At Warmy, our research team continues to do more by figuring out how to get more of your emails delivered, straight to your intended inbox. Our ongoing testing and analysis […]
SSL and TLS Certificate Errors in Email Servers: How They Impact Deliverability
What if you were to send an important email—a client proposal, let’s say, or a security update, or internal memo—and it was rejected, marked as spam, or even intercepted? That’s where SSL/TLS encryption comes in. These protocols secure email traffic through data encryption and confirmation of the authenticity of mail servers. But SSL/TLS encryption doesn’t work […]
The Challenges of SMTP over IPv6: What You Need to Know Before Transitioning
SMTP (Simple Mail Transfer Protocol) has been the staple of email communication for the last couple of decades—forwarding messages over networks via the Internet Protocol, which has, until recently, been IPv4. But exhaustion of IPv4 addresses is gradually pushing businesses and email service providers to think about moving to SMTP over IPv6. It provides a nearly infinite […]
