Postscale

What Postscale is

Postscale is an email API for developers that puts three jobs behind one account: sending transactional email, receiving and parsing inbound mail, and giving users masked addresses that forward to their real inboxes. The home page sums it up as "The email API for sending, inbound, and privacy" and adds "One API." Around that core sit a DMARC reporting API and an e-invoicing API for the German and wider EU market. The service is operated by DNScale OÜ, which the site places in Estonia, and the same makers run DNScale managed DNS and AttribIQ, a web analytics and revenue attribution tool.

The site says primary production service data is hosted in the EU/EEA, and that limited network, device and operational metadata may be processed by infrastructure providers under appropriate transfer safeguards. It signs a standard GDPR DPA and publishes a subprocessor list. Postscale is built for the mail an application sends and receives, not for designing marketing campaigns.

Sending

Mail goes out through a REST API or an SMTP relay, which the home page describes as "one sending pipeline". Official SDKs cover Node.js, Python, Ruby, PHP and Go, and the Node package installs from npm as @postscale/postscale, with examples for Next.js, Express, Hono and Bun. The sample call sends a message with from, to, subject and an HTML body and returns a message ID or an error object, so the code checks one result rather than wrapping raw HTTP. The SDKs also verify signed webhooks.

The sending side lists DKIM, SPF, DMARC, suppressions and IP warming, plus signed webhooks for delivery and bounce events, so each message can be followed from acceptance to delivery, bounce or retry. The Starter, Plus and Pro plans list custom DKIM signing. The site stresses scoped API keys, "predictable resources" and practical migration guides.

Migration is treated as a project of its own. The home page lays out three steps: prepare (verify domains, authentication, suppression data and sending limits), run in parallel (move one stream at a time while both providers stay observable) and scale deliberately (warm traffic, watch bounces, retire the old route). A migration center collects the guides, and the sales team offers migration planning for larger accounts.

Inbound email

To receive mail, a customer points an MX record at mx.postscale.io with priority 10 and verifies ownership through a TXT record. The inbound page says the full setup is four DNS records and takes about five minutes. From then on each message reaches the application as a signed JSON webhook with parsed headers, the plain-text and HTML bodies, attachment metadata, download links and sender details, so there is no MIME parsing on the customer's side.

Attachments stay out of the webhook body. They are stored separately and exposed through authenticated Postscale download URLs, which the application fetches with its API credentials and copies to its own storage if it needs longer retention. Routing can be catch-all for a whole domain or pattern-based per address, such as a plus-addressed support alias that carries a ticket number. Rules per domain can block senders, reject by subject pattern, auto-respond or route to different endpoints, and they run before the webhook fires. Webhooks are signed with HMAC and retried with exponential backoff for 4 attempts. Built-in reply detection reads the In-Reply-To and References headers, so the application knows which outbound message a reply belongs to.

Masked addresses with Postscale Shield

Postscale Shield generates unique, revocable aliases that forward to a user's real inbox. The site describes it as an API a product embeds "on your own domain, for all your users regardless of platform". One API call creates one address. An alias can forward to a single inbox or to a team, the destination can change without breaking the alias, and disabling it is one call that stops forwarding without deleting anything. Aliases run on the shared shield.postscale.io subdomain, which is available for free accounts and quick starts, or on shield.yourdomain.com once the customer adds an MX record and a couple of DNS entries.

Forwarding applies the Sender Rewriting Scheme so SPF stays valid through the hop. Per-alias analytics show which aliases still receive mail, which are silent and which senders hit each one. Limits per alias and per sender are configurable, and unusually high inbound volume on one alias fires a webhook so it can be disabled before it hurts deliverability. The FAQ says disabled aliases are free to retain: Postscale keeps them inert rather than deleting them, so re-enabling is one call.

DMARC reporting and e-invoicing

The DMARC Reporting API receives aggregate (RUA) reports at an address Postscale provides, or accepts existing XML reports posted to the API, and returns structured JSON by source IP, DKIM and SPF alignment and policy outcome. Per-domain dashboards group results by sending domain, webhooks fire when a new IP starts sending under the domain or a pass rate crosses a threshold, and a trend API tracks progress from p=none to quarantine to reject. Forensic (RUF) reports are on the roadmap. DMARC reporting is included on paid plans only.

The XRechnung API validates, sends and receives electronic invoices in XRechnung, ZUGFeRD and Factur-X, all described as EN 16931 compliant. Invoices go out by email as signed XML attachments or embedded PDFs, and inbound invoices arrive at a dedicated address as JSON with line items, totals, VAT and buyer and seller IDs. The site notes that since 2025-01-01 all German businesses must be able to receive E-Rechnung, with sending phased in through 2028. A sandbox supports full validation and a limited number of real sends.

Plans and pricing

Every plan draws sending and receiving from one shared monthly allowance. Outbound mail counts per accepted recipient, including To, Cc and Bcc, and inbound counts per accepted message. The Free plan, "Free forever", includes 1,000 shared send and receive emails a month, 10 masked addresses, basic inbound parsing, a basic usage counter, self-serve documentation and 1 domain, with no credit card required.

• Starter, €9 a month: 10,000 shared emails, extra emails at €1.20 per 1,000, 50 masked addresses, 5 domains, analytics dashboard, best-effort product support.
• Plus, €29 a month, marked most popular: 50,000 shared emails, extra emails at €1.00 per 1,000, 150 masked addresses, 10 domains.
• Pro, €79 a month: 100,000 shared emails, extra emails at €1.00 per 1,000, 500 active masked addresses, 25 domains, priority best-effort support.
• Scale, €329 a month: 500,000 shared emails, extra emails at €0.80 per 1,000, 5,000 active masked addresses, unlimited domains, a dedicated IPs add-on and advanced analytics.

Monthly prices are shown; annual billing takes 17% off. Prices exclude VAT where applicable, and tax appears at checkout. Plans can be changed at any time, with prorated changes taking effect immediately. For higher volume, dedicated infrastructure, compliance requirements or more aliases, the pricing page points to the sales team.

Who it suits

Postscale suits developers who want sending, receiving and user privacy in one API with one bill, particularly SaaS products that run a support inbox, parse replies or hand users throwaway addresses at signup. Companies that want their primary service data held in the EU/EEA by an EU operator have a clear statement to work from. German and EU billing software gains e-invoicing from the same vendor. The free plan is enough to build and test a prototype. A marketing team looking for a campaign editor and subscriber lists would pair it with a separate tool.