Email testing, deliverability, and API guides

Mastering Email Marketing: Promote Your Business with the Inbox. Find out how to educate your audience, increase your ROI, and avoid spamming tactics.

Email testing

Testing Content Security Policy (CSP) Headers

6 min read

Lock down your website's security with modern content-security-policy (CSP) headers. Learn how to add and test CSP in this informative post.

Email testing

Telnet SMTP Testing: How to Test SMTP with Telnet and OpenSSL

Use telnet SMTP checks and OpenSSL STARTTLS tests to validate SMTP connectivity, response codes, and TLS posture before inbox-delivery tests.

SGMailSlurp field guide

Stripe get all customers list (example)

Fetching All Customers from Stripe: A Quick Tutorial Using Their API in Kotlin, Paginating batches of 100 until all customers are retrieved.

SMTP protocol explained: commands, response codes, ports, and examples

Learn SMTP protocol basics with command flow, SMTP response codes, port guidance, and secure implementation examples for developers.

SMTP encryption guide: TLS, STARTTLS, and secure SMTP setup

10 min read

Understand SMTP encryption and how to secure mail transfer with TLS, STARTTLS, authentication, and domain alignment controls.

SSMailSlurp field guide

SMS & OTP

SMS Short Codes Explained: Dedicated vs Shared and 10DLC Tradeoffs

Learn what SMS short codes are, when to use dedicated short codes, and how they compare with 10DLC and toll-free messaging.

SMS & OTP

SMS OTP Verification: Token Design, Delivery Flow, and Abuse Controls

Design robust SMS OTP verification with secure token handling, resend rules, regional delivery strategy, and conversion-aware monitoring.

SIMailSlurp field guide

SMS & OTP

SMS Intercept Attacks and Why SMS Multi-Factor Still Matters

The Risks and Rewards of SMS-Based Multi-Factor Authentication: A Critical Analysis of Security Vulnerabilities and User-Friendliness.

STMailSlurp field guide

Email design

Set the same CSS property twice in React

4 min read

React style props use JavaScript objects, so duplicate keys cannot provide CSS fallbacks. Learn when to use a class, image-set(), or picture instead.

Send Email with JavaScript: Browser, Node.js, and Email API Patterns

5 min read

Send email with JavaScript from Node.js or a browser-backed API without exposing credentials. Includes Nodemailer, MailSlurp, and delivery checks.

Send email in Swift: iOS composer and MailSlurp API

6 min read

Choose the right Swift email path: open Apple's iOS mail composer for a person to send, or use MailSlurp to send and test real email from a trusted backend or test target.