SendHQ resources
Email API guides for product teams
Clear, implementation-focused answers about transactional email, inbound routing, deliverability, domains, and AI-agent workflows.
Amazon SES Cost: A Product Team Pricing Model
Model Amazon SES cost across recipients, data, pricing plans, dedicated IPs, event infrastructure, quotas, and the engineering layer around delivery.
Read page →Amazon SES: What Application Teams Need to Operate
Understand Amazon SES identities, regions, APIs, quotas, events, suppressions, and the application controls a production email system still needs.
Read page →How to Check an SPF Record for Application Email
Check the correct SPF domain, syntax, mechanisms, nested DNS budget, source-IP authorization, result, and DMARC alignment for application email.
Read page →How to Check DKIM for Application Email
Check DKIM by inspecting a real signature, querying its selector and domain, verifying the message, reading receiver results, and testing alignment.
Read page →How to Configure DMARC in Cloudflare Safely
Configure Cloudflare DMARC from an audited sender inventory, validate aligned authentication, review reports, and stage policy changes with rollback.
Read page →Cloudflare Email Routing: Safe Setup Guide
Set up Cloudflare Email Routing with verified destinations, explicit rules, bounded Workers, safe MIME handling, observability, and tested rollback.
Read page →DKIM Setup Guide for Product Email
Set up DKIM with owned signing domains, protected private keys, explicit selectors, controlled signing paths, verification tests, rotation, and DMARC alignment.
Read page →How to Run a DMARC Check for Application Email
Check DMARC record discovery, syntax, SPF and DKIM alignment, policy, reports, and real application messages without confusing a DNS lookup with delivery.
Read page →Email API Implementation Guide for Product Teams
Design a safe email API integration with verified domains, queued sends, stable identifiers, controlled retries, delivery events, suppression, and tenant isolation.
Read page →Email Bounce-Back Troubleshooting for Product Teams
Handle email bounce-backs by preserving SMTP and DSN evidence, separating temporary from permanent failures, suppressing unsafe retries, and reconciling outcomes.
Read page →How to Evaluate an Email Deliverability Service
Evaluate email deliverability services by scope, evidence, authentication, feedback loops, suppressions, privacy, portability, and operational fit.
Read page →How to Evaluate an Email Validation Service
Evaluate email validation services by syntax, DNS, SMTP evidence, uncertainty, privacy, freshness, consent boundaries, APIs, and operational fit.
Read page →How to Evaluate a Free SMTP Service
Evaluate free SMTP services by real workload limits, expiry and overage terms, TLS and authentication, domain setup, events, suppressions, support, and exit cost.
Read page →Gmail API Implementation Guide for Product Teams
Implement Gmail API access with least-privilege OAuth, durable mailbox sync, safe sending, bounded retries, and a clear service-account model.
Read page →Google SMTP Relay Service Evaluation Guide
Evaluate Google Workspace SMTP relay by authorization model, TLS, sender identity, quotas, error handling, authentication, observability, and migration risk.
Read page →Mailgun API Implementation Guide for Product Teams
Implement Mailgun with verified domains, scoped credentials, durable send jobs, authenticated webhooks, precise events, and suppression-aware workflows.
Read page →SMTP Mail Protocol: How Application Email Moves
Learn how SMTP submission, relay, envelopes, response codes, TLS, retries, and message content shape an application email workflow.
Read page →Office 365 SMTP Details for Applications
Understand Microsoft 365 SMTP client submission, connector relay, Direct Send, OAuth, TLS, hosts, ports, identities, limits, and application tradeoffs.
Read page →Postmark API Implementation Guide for Product Teams
Implement Postmark with server-scoped tokens, verified senders, durable jobs, explicit message streams, exact API outcomes, secure webhooks, and suppressions.
Read page →Python 3 SMTP: Safe Production Implementation
Implement Python SMTP with EmailMessage, verified TLS, server-only secrets, explicit envelopes, durable jobs, partial-recipient handling, and bounded retries.
Read page →Resend Email API Implementation Guide for Product Teams
Implement the Resend email API with verified domains, scoped keys, idempotent sends, signed webhooks, durable events, and honest delivery states.
Read page →SendGrid API Implementation Guide for Product Teams
Implement SendGrid with authenticated domains, scoped API keys, durable send records, verified event webhooks, and suppression-aware workflows.
Read page →SMTP Ports 25, 465, and 587: A Practical Guide
Choose the right SMTP port by role and TLS mode, then diagnose connection, handshake, authentication, and message acceptance failures.
Read page →Safe SMTP Email Sending with Python
Implement Python SMTP sending with durable jobs, EmailMessage, authenticated TLS, bounded timeouts, exact recipient outcomes, and evidence-driven retry handling.
Read page →How to Evaluate an SMTP Relay Service
Evaluate SMTP relay services by submission security, authentication, queues, retry behavior, limits, delivery events, suppression, isolation, and migration fit.
Read page →SPF Record Syntax Explained for Application Email
Understand SPF v=spf1 syntax, mechanisms, qualifiers, modifiers, DNS lookup limits, include and redirect behavior, validation, and DMARC alignment.
Read page →Yahoo Mail Authentication Failed: Diagnostic Guide
Diagnose Yahoo authentication failures by preserving SMTP evidence, separating temporary and permanent replies, and testing SPF, DKIM, DMARC, and alignment.
Read page →Email API: Send, Receive, and Track Transactional Email
Understand what an email API does, how sending and inbound receiving work, and what to evaluate before choosing one.
Read guide →Transactional Email API Guide
A practical guide to sending passwords, receipts, alerts, and other product-triggered email reliably.
Read guide →How to Send Email with an API
A step-by-step approach to authenticated API email sending, testing, and production safety.
Read guide →How to Receive Email with an API
Route inbound mail to your application, parse it safely, and make it useful in a product workflow.
Read guide →Email Domain Verification: SPF, DKIM, and DMARC
What domain verification is, why it matters, and how SPF, DKIM, and DMARC work together.
Read guide →Improve Email Deliverability: Issues, Factors, and Monitoring
How to improve email deliverability: the factors that decide inbox placement, common deliverability problems, and how to monitor delivery rates.
Read guide →Inbound Email Webhooks: Design Patterns and Safety
Use webhooks to process inbound messages without building a polling mailbox workflow.
Read guide →Email API for AI Agents
Give agents a constrained, observable way to send and receive product email without exposing mailbox credentials.
Read guide →Amazon SES API: A Practical Integration Guide
Use Amazon SES for application email while keeping your provider layer, domains, and observability under your control.
Read guide →Resend Alternative: What to Compare
A neutral checklist for comparing developer-focused email platforms without migrating blindly.
Read guide →KingSMTP Alternative: Monero-Payable Email API with MCP
Compare SendHQ with KingSMTP. Both accept Monero; SendHQ adds an MCP server for AI agents, a CLI, OpenAPI 3.1, inbound inboxes, and hosted templates.
Read guide →Maileroo Alternative: Email API with MCP, Payable in Monero
Compare SendHQ with Maileroo. Both take crypto; SendHQ also takes Monero and adds an MCP server for AI agents, a CLI, and an OpenAPI 3.1 contract.
Read guide →Email API with Node.js
A server-side pattern for sending transactional email from Node.js without leaking API keys.
Read guide →Email API with Python
A backend-safe pattern for transactional email from Flask, Django, FastAPI, or a worker.
Read guide →Email Bounce Handling for Product Teams
Classify bounces, suppress unsafe recipients, and keep critical product email observable.
Read guide →SPF, DKIM, and DMARC Explained
A plain-language explanation of the DNS records that establish email authentication and alignment.
Read guide →Transactional Email vs Marketing Email
Understand the different consent, content, and reputation requirements for product messages and campaigns.
Read guide →How to Evaluate Email API Pricing
Compare email API pricing by capabilities and operational fit, not only by messages per month.
Read guide →Competitor reviews
Sourced summaries of what users say about other providers.