Developer Guides

Step-by-step guides for email delivery, authentication, API integration, and deliverability optimization.

Getting Started

Send transactional email from Node.js using the RelayPost API.

Send transactional email from Python using the RelayPost API.

Design, deliverability, and timing patterns for transactional email.

How SPF, DKIM, and DMARC work together to protect your domain.

Create and publish an SPF record to authorize your sending servers.

Generate DKIM keys and add the DNS record for message signing.

Configure a DMARC policy to enforce authentication and get reports.

Everything that affects whether your email reaches the inbox.

Actionable steps to increase inbox placement rates.

Identify and fix the causes of hard and soft bounces.

Diagnose and fix spam folder placement issues.

How ISPs score your domain and what affects the score.

Gradually ramp sending volume on a new domain or IP.

Compare email APIs for Node.js projects and pick the right one.

Compare email APIs for Python projects and pick the right one.

Which port to use for SMTP submission, relay, and encryption.

Reference for common SMTP response codes and what they mean.

Fix the 10-lookup SPF limit with flattening and optimization.

Debug DKIM signature failures, key mismatches, and DNS issues.

RelayPost handles authentication, deliverability, and tracking. Start free.