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SMTP Labs

smtp.dev

From $7/mo Free plan WebAPI
Visit smtp.dev
Spec score 8.4 #8 of 28 in Email Testing Software

What it is

SMTP Labs is an email testing service that receives test messages over SMTP and lets you inspect them on the web, through IMAP or POP3, or via an API. Messages remain in a sandbox and cannot reach external recipients. Inspection includes HTML and plain text, headers, MIME structure, raw source, and attachments. SPF, DKIM, and DMARC checks appear in the interface and API, while a deliverability audit reviews sender configuration, HTML, links, and content patterns associated with spam filters. The REST API covers domains, accounts, mailboxes, messages, and tokens; server-sent events can push new messages. SMTP, IMAP, and POP3 work without a vendor SDK. The Lite plan is free at free with one domain, 50 accounts, and seven-day retention. Pro costs $7 a month, and Max costs $20 a month, with longer retention and expanded domains or accounts. Email and account data are primarily processed in the United States.

Spec sheet

What it does
SMTP Labs is a hosted email-testing sandbox where inbound messages can be inspected through a web interface, IMAP, POP3, or REST API.Read 15 Oct 2026 · smtp.dev
Purpose
SMTP Labs is an email testing service that receives test email over SMTP and lets users inspect it through the web UI, IMAP, POP3, or API.Read 3 Oct 2026 · smtp.dev
Integrations
The maker documents CI use with GitHub Actions, Jenkins, GitLab CI, and CircleCI, using standard SMTP and the REST API.Read 3 Oct 2026 · smtp.dev
Support
The terms state the company has no support or maintenance obligation except as may be included in a paid subscription plan.Read 3 Oct 2026 · smtp.dev
Account deletion
Users can request account deactivation, but full account deletion is unavailable because of anti-abuse obligations.Read 3 Oct 2026 · smtp.dev
API and realtime
The REST API covers domains, accounts, mailboxes, messages, and tokens; new messages can be pushed through server-sent events.Read 3 Oct 2026 · smtp.dev
API authentication
API requests use an X-API-KEY header, and newly created token values are shown only once.Read 15 Oct 2026 · smtp.dev
API rate limit
The documented limit is 4,096 requests per minute per authenticated user, with HTTP 429 responses when exceeded.Read 15 Oct 2026 · smtp.dev
Authentication checks
Every received message can show SPF, DKIM, and DMARC verification results in the interface and API.Read 15 Oct 2026 · smtp.dev
Catch-all accounts
A wildcard account can capture mail for otherwise uncreated addresses on a domain.Read 15 Oct 2026 · smtp.dev
CI integrations
Documentation provides examples for GitHub Actions, Jenkins, GitLab CI, and CircleCI using SMTP plus the REST API.Read 15 Oct 2026 · smtp.dev
Client compatibility
Thunderbird and Apple Mail can connect over IMAP, while webmail is available at webmail.smtp.dev.Read 15 Oct 2026 · smtp.dev
Custom domains
Users add domains or subdomains and point their MX records to mx.smtp.dev to receive test mail.Read 15 Oct 2026 · smtp.dev
Data location
The privacy policy says email content and account information are primarily stored and processed in the United States, with safeguards for international transfers.Read 15 Oct 2026 · smtp.dev
Deliverability audit
Its audit checks sender configuration, subject, HTML structure, links, images, and content patterns associated with spam filtering.Read 15 Oct 2026 · smtp.dev
Documentation depth
The site publishes API reference, setup pages, feature pages, CI and E2E guides, an llms.txt index, and markdown versions of documentation pages.Read 15 Oct 2026 · smtp.dev
Domains and aliases
Users can bring custom domains and subdomains, use catch-all accounts, and route plus-sign aliases.Read 3 Oct 2026 · smtp.dev
End-to-end testing
A Playwright guide demonstrates triggering a password reset, retrieving the email through the API, extracting its link, and completing the flow.Read 15 Oct 2026 · smtp.dev
Independent article date
SMTPedia published its smtp.dev assessment on 11 July 2026.Read 15 Oct 2026 · smtpedia.com
Independent classification
SMTPedia classifies smtp.dev as a throwaway email provider and says it had tracked 361 rotating domains since approximately 2021.Read 15 Oct 2026 · smtpedia.com
Independent criticism: abuse patterns
SMTPedia claims smtp.dev addresses appear in free-tier abuse, referral farming, crypto-airdrop sybil activity, and chargeback-fraud patterns.Read 15 Oct 2026 · smtpedia.com
Independent criticism: abuse risk
SMTPedia says the provider's programmatic address creation and inbox polling indicate potential bot-grade abuse and recommends blocking or extra verification for its addresses.Read 15 Oct 2026 · smtpedia.com
Independent DNS finding
DNSCheck.pro observed Cloudflare authoritative nameservers and an MX record pointing to mx.yandex.net for smtp.dev.Read 15 Oct 2026 · dnscheck.pro
Independent DNS limit
DNSCheck.pro reported that smtp.dev lacked a DMARC record at the time of its September 2025 scan.Read 15 Oct 2026 · dnscheck.pro
Independent DNS report date
DNSCheck.pro's report for smtp.dev was generated on 25 September 2025.Read 15 Oct 2026 · dnscheck.pro
Independent mail test
DNSCheck.pro's scan found the domain's mail server rejected [email protected] but accepted [email protected].Read 15 Oct 2026 · dnscheck.pro
Licence
The terms grant a limited, revocable, non-transferable license for personal or internal business use and prohibit copying, reverse engineering, hosting, or commercial exploitation.Read 15 Oct 2026 · smtp.dev
Limit: account deletion
Full account deletion is unavailable; profile information is removed after deactivation while operational records may be retained indefinitely in anonymized or pseudonymized form.Read 15 Oct 2026 · smtp.dev
Limit: external delivery
The service cannot send outbound test messages to real external recipients, so it is unsuitable for testing production-recipient delivery.Read 15 Oct 2026 · smtp.dev
Mailbox structure
New accounts start with Inbox, Sent, Drafts, Trash, and Junk mailboxes, and users can add custom mailboxes.Read 15 Oct 2026 · smtp.dev
Message inspection
Messages can be viewed as HTML or plain text and examined as MIME structures, headers, attachments, or complete RFC 5322 source.Read 15 Oct 2026 · smtp.dev
Plus addressing
Plus-sign aliases such as [email protected] deliver to the base account while preserving the alias in the recipient data.Read 15 Oct 2026 · smtp.dev
Privacy rights
The policy describes access, correction, erasure, portability, restriction, objection, and consent-withdrawal rights for covered users.Read 15 Oct 2026 · smtp.dev
Protocols
The service supports SMTP for sending test mail, IMAP and POP3 for retrieval, and API access.Read 15 Oct 2026 · smtp.dev
Public API
The REST API exposes domains, accounts, mailboxes, messages, and tokens through an OpenAPI v3-described interface.Read 15 Oct 2026 · smtp.dev
Real-time events
New account, mailbox, and message changes can be streamed through Mercure server-sent events.Read 15 Oct 2026 · smtp.dev
Retention
Message retention depends on the plan and can be up to 90 days, with shorter per-message expiry available.Read 3 Oct 2026 · smtp.dev
Sandbox
The service receives real email but sends only within its sandbox, so test messages cannot reach external recipients.Read 3 Oct 2026 · smtp.dev
Sandbox boundary
Outbound messages are restricted to accounts inside the SMTP Labs sandbox and cannot reach external recipients.Read 15 Oct 2026 · smtp.dev
SDK position
The product advertises standard protocols and says no vendor SDK is required; its API page invites community SDKs rather than listing official SDK packages.Read 15 Oct 2026 · smtp.dev
Security and email data
The privacy policy says it uses encryption, firewalls, and SSL technology, and does not use email content for advertising or unrelated purposes.Read 3 Oct 2026 · smtp.dev
Security controls
The privacy policy says the service uses encryption, firewalls, SSL technology, and third-party authentication protections.Read 15 Oct 2026 · smtp.dev
System setup
Inbound testing requires adding an MX record named @ or a subdomain that points to mx.smtp.dev; DNS propagation may take 24 hours or longer.Read 15 Oct 2026 · smtp.dev
Technology stack
The API documentation identifies API Platform, Mercure, Nuxt.js, Haraka, Caddy, MongoDB, Node.js, and Rocky Linux in the service stack.Read 15 Oct 2026 · smtp.dev

Plans and prices

Lite Free monthly 1 domain · 50 accounts · 7-day message retention · SMTP, IMAP, POP3, API · email audit Read 15 Oct 2026 · smtp.dev
Pro $7 a month monthly 5 domains · 25,000 accounts · 30-day message retention · SMTP, IMAP, POP3, API · email audit · catch-all and aliasing Read 15 Oct 2026 · smtp.dev
Max $20 a month monthly Unlimited domains · unlimited accounts · 90-day message retention · SMTP, IMAP, POP3, API · email audit · catch-all and aliasing Read 15 Oct 2026 · smtp.dev

Every SMTP Labs plan and price →

Strong points and limits

Strong points

  • Sandbox prevents delivery to external recipients
  • Inspects message content, structure, and attachments
  • SPF, DKIM, and DMARC checks included
  • REST API and realtime message events
  • Free Lite plan available

Limits

  • Sandbox messages cannot reach external recipients
  • Lite retention is limited to seven days
  • Full account deletion is unavailable
  • Paid plans start at $7 a month

Who it suits

It suits developers and QA teams that need sandboxed email capture, protocol access, deliverability checks, and CI integrations. The service documents use with GitHub Actions, Jenkins, GitLab CI, and CircleCI.

Verdict

SMTP Labs provides protocol-based email capture with detailed inspection, authentication checks, audits, and automation APIs. Choose a plan based on required domains, accounts, and retention, and note the sandbox and deletion constraints.

Where Specifiction places it

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