550 5.1.1 User unknown is a server error response code to RCPT TO command. Learn what it means, how to fix and avoid this issue on different servers
SMTP relay is the process of routing emails to the proper destination SMTP server. Check out several options to test your SMTP server for relaying
Mailcatcher can be used to test your emails before they’re sent to real users. Let's see how it works and what are the available alternatives.
MailHog is a fake SMTP server for testing the email sending of web apps. Find out how to set it up and use it, as well as the best alternatives to MailHog.
There's plenty of reasons to hide emails. Some obfuscate them to avoid spam bots. Others mask emails to test their workflows or secure database records. Let's see what really works and what doesn't.
QAs often create tons of fake email addresses to test their workflows. How to go about it? Which tools to use? And is it the right approach? Let's see!
The email testing checklist includes test of email sending capability, deliverability and content. Check out our picks of tools to cover all types of tests
Have you ever sent test emails to your customers by an accident? You are not alone! Check out our TOP-5 email testing failures and learn some tips on how to stay on the safe side!
In our previous post, we reviewed Sendgrid, Mandrill, and Mailgun - the most popular email sending services. “Test your emails before actually sending them”: each of them repeats this mantra, as does anyone who deals with email development. But do these services offer enough options for quality email testing? Let’s have a closer look at the checkpoints and see if there is a need for a special testing service.
How to embed images in HTML emails properly? CID attachment, inline embedding, linked image, or any new technique? Read in our overview along with email testing tips.