2026-07-14 · 1 min read
Warming up a new sending domain without losing deliverability
A practical warm-up schedule for a new sending domain: volume ramps, engagement signals, and the authentication records to land in the inbox instead of spam.
Blog author
Administrator
PulsePigeon
Published on behalf of the PulsePigeon team.
2026-07-28 · 1 min read
Designing idempotent sends with the PulsePigeon email API
How to use idempotency keys when sending transactional email so retries after a timeout never result in a duplicate message reaching a customer.
2026-08-26 · 1 min read
How we automated dedicated-IP warm-up without overloading reputation
An engineering writeup of PulsePigeon's dedicated-IP warm-up automation: per-IP stage state, reputation gates, bounded evaluation, and fail-closed rollout controls.
2026-08-26 · 1 min read
A practical IP warming schedule you can hand to a new customer
A practical guide to PulsePigeon's staged dedicated-IP volume caps, reputation thresholds, minimum dwell, and safe pauses when a gate is not met.
2026-08-26 · 2 min read
SPF too many DNS lookups: diagnose and fix the limit
The SPF 10-lookup limit is one of the most common authentication failures. What causes it, what the error looks like, and the practical fixes that don't break your existing email flow.
2026-08-26 · 2 min read
DKIM selector not found: diagnose and repair
When a DKIM check fails with 'selector not found', the receiving server could not resolve the public key. Walk through the common causes and the verification steps.
2026-08-26 · 1 min read
DMARC quarantine vs reject — what to pick at each ramp stage
How to choose between DMARC policies p=none, p=quarantine, and p=reject as you move a new domain from monitoring into enforcement. The trade-offs and the failure modes.
2026-08-26 · 1 min read
SMTP 550 — permanent failure codes and what to do with each
A 550 response means the mailbox rejected the message and is asking you not to retry. Decode the common sub-codes and the right operational response for each.
2026-08-26 · 1 min read
SMTP 421 — transient failure retry strategy
A 421 response is a temporary failure: the receiving server is asking you to retry later. The right retry policy protects your sender reputation and your recipients' patience.
2026-08-26 · 2 min read
Send transactional email from Next.js with the REST API
A server-only Next.js REST example for order receipts, with stable idempotency, accepted message IDs, error handling, and delivery-event follow-up.
2026-08-26 · 1 min read
Planning a transactional email send from FastAPI
Conceptual guidance for server-side sends from FastAPI, including idempotency, response handling, and when a durable worker is safer than BackgroundTasks.
2026-08-26 · 1 min read
Sending transactional email from a Node.js app with PulsePigeon
Wire a PulsePigeon send into a Node.js HTTP handler or a BullMQ worker. Idempotency keys, error handling, and a typed error model.
2026-08-26 · 1 min read
Sending transactional email from a Python app with PulsePigeon
The Python SDK pattern: synchronous and asynchronous clients, deterministic idempotency keys, status-specific errors, and application-owned retries.
2026-08-26 · 1 min read
SMTP relay, explained — and why free public relays are not safe for production
What an SMTP relay does, how it differs from a transactional email API, and why the free public SMTP relays that come up in search results are a reputation risk you cannot afford.
2026-10-20 · 3 min read
Diagnose email authentication and alignment from a real message
A reproducible checklist for comparing SPF, DKIM and DMARC DNS records with the identities in an authorized received email, and for telling authentication from alignment.
2026-10-20 · 4 min read
Verify signed webhooks and store each event once
A tested Python example that verifies a PulsePigeon signed status event, stores a receipt once, rejects a reused event ID with different content, and keeps send idempotency separate from event idempotency.
2026-08-26 · 1 min read
Best transactional email APIs compared (2026 Q3)
A disclosed, criteria-based guide to evaluating Resend, Mailgun, SendGrid, Amazon SES, and PulsePigeon for transactional email.
2026-08-26 · 1 min read
Best bulk email services compared (2026 Q3)
A criteria-based guide to evaluating Mailchimp, Kit, Brevo, Mailgun, SendGrid, and PulsePigeon for campaigns and broadcasts.
2026-08-26 · 1 min read
Email API evaluation checklist for developers
A repeatable integration checklist for evaluating email APIs: request contracts, error handling, retries, signed events, and release verification.
2026-08-26 · 1 min read
Best email service provider for developers (2026 Q3)
A practical provider-evaluation worksheet for developer-heavy teams comparing Resend, Mailgun, SendGrid, Amazon SES, and PulsePigeon.
2026-08-26 · 1 min read
Best email service provider for SaaS (2026 Q3)
A SaaS-focused framework for comparing Mailgun, SendGrid, Customer.io, and PulsePigeon without unsupported rankings.
2026-08-26 · 1 min read
Best email service provider for startups (2026 Q3)
A startup-oriented framework for comparing Resend, Mailgun, SendGrid, Amazon SES, and PulsePigeon by evidence, cost, and operational load.
2026-08-26 · 1 min read
Best email service provider: the full comparison (2026 Q3)
A consolidated decision framework for comparing email service providers across developer, SaaS, startup, transactional, and campaign needs.