SendStreak Academy

Short, technical explanations of email infrastructure concepts — from protocols and authentication to deliverability and automation.

The anatomy of email headers

SendStreak Academy

Explore the technical structure of email headers. Learn how to decode metadata, routing paths, and authentication results like SPF or DKIM.

What are SMTP status codes?

SendStreak Academy

A developer reference for SMTP status codes. Learn what 250, 354, 421, 450, 550, and other reply codes mean and how to handle them in your application.

What is DKIM (DomainKeys Identified Mail)?

SendStreak Academy

Learn how DKIM uses cryptographic signatures to verify email authenticity and prevent tampering, and how to set it up for your sending domain.

What is DMARC?

SendStreak Academy

Learn how DMARC builds on SPF and DKIM to prevent email spoofing, with a practical guide to DMARC policies, alignment, and reporting.

What is SMTP relay?

SendStreak Academy

Learn what SMTP relay is, how it differs from direct sending, and why relay services improve email deliverability for transactional and application email.

What is SMTP?

SendStreak Academy

Learn about SMTP (Simple Mail Transfer Protocol), the standard application-layer protocol for sending and relaying outgoing email from a client to a server.

What is SPF (Sender Policy Framework)?

SendStreak Academy

Learn how SPF works, why it matters for email deliverability, and how to configure an SPF DNS record to authorize your sending servers.

What is TLS/STARTTLS in email?

SendStreak Academy

Learn how TLS and STARTTLS encrypt email in transit. Covers implicit TLS vs opportunistic TLS, which SMTP ports to use, and how to configure your app.

What is a transactional email?

SendStreak Academy

A technical definition of transactional email, explaining how automated, one-to-one messages like password resets and receipts are triggered and sent.

What's the difference between SMTP, IMAP, and POP3?

SendStreak Academy

Understand the key differences between email protocols. Learn how SMTP (sending), IMAP (syncing), and POP3 (retrieving) work together to manage your email.