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SMTP Labs
What it is
SMTP Labs is an email testing service for receiving test messages over SMTP and examining them through a web interface, IMAP, POP3, or an API. Messages stay inside its sandbox, so they cannot be sent to outside recipients. You can inspect HTML and plain text, headers, MIME structure, raw source, and attachments. SPF, DKIM, and DMARC checks appear in the interface and through the API. A deliverability audit reviews sender configuration, HTML, links, and content patterns associated with spam filters, grouping findings by severity. The REST API covers domains, accounts, mailboxes, messages, and tokens, while server-sent events can notify systems about new messages. SMTP, IMAP, and POP3 work without a vendor SDK. Custom domains, subdomains, catch-all accounts, and plus-sign aliases are supported. Retention varies by plan, up to 90 days. Plans include Lite at no cost, Pro at $7 a month, and Max at $20 a month.
For and against
For
- Supports SMTP, IMAP, POP3, and API access
- Inspects headers, MIME, source, and attachments
- Includes SPF, DKIM, and DMARC checks
- Deliverability audit reviews spam-related patterns
- Supports custom domains and catch-all accounts
Against
- Sandbox messages cannot reach external recipients
- Full account deletion is unavailable
- Support obligations may exclude unpaid plans
- Retention depends on plan
The verdict
SMTP Labs combines protocol access, message inspection, authentication checks, and deliverability review in one testing service. Its free Lite plan provides a starting point, while paid plans add more domains, accounts, and retention.
Who it suits
It suits developers and teams testing email delivery, message content, authentication, and integrations through web tools or APIs. CI users can connect it with GitHub Actions, Jenkins, GitLab CI, or CircleCI.
Plans and prices
Lite
1 domain · 50 accounts · 7-day message retention · SMTP, IMAP, POP3, API
Read 15 Oct 2026 · smtp.dev
Pro
5 domains · 25,000 accounts · 30-day message retention · SMTP, IMAP, POP3, API
Read 15 Oct 2026 · smtp.dev
Max
Unlimited domains · unlimited accounts · 90-day message retention · SMTP, IMAP, POP3, API
Read 15 Oct 2026 · smtp.dev
On the record
- Account deletion
- Users can request account deactivation, but full account deletion is unavailable because of anti-abuse obligations.smtp.dev · read 3 Oct 2026
- API and realtime
- The REST API covers domains, accounts, mailboxes, messages, and tokens; new messages can be pushed through server-sent events.smtp.dev · read 3 Oct 2026
- API authentication
- API requests use an X-API-KEY header, and newly created token values are shown only once.smtp.dev · read 15 Oct 2026
- API rate limit
- The documented limit is 4,096 requests per minute per authenticated user, with HTTP 429 responses when exceeded.smtp.dev · read 15 Oct 2026
- Authentication checks
- Every received message can show SPF, DKIM, and DMARC verification results in the interface and API.smtp.dev · read 15 Oct 2026
- Catch-all accounts
- A wildcard account can capture mail for otherwise uncreated addresses on a domain.smtp.dev · read 15 Oct 2026
- CI integrations
- Documentation provides examples for GitHub Actions, Jenkins, GitLab CI, and CircleCI using SMTP plus the REST API.smtp.dev · read 15 Oct 2026
- Client compatibility
- Thunderbird and Apple Mail can connect over IMAP, while webmail is available at webmail.smtp.dev.smtp.dev · read 15 Oct 2026
- Custom domains
- Users add domains or subdomains and point their MX records to mx.smtp.dev to receive test mail.smtp.dev · read 15 Oct 2026
- 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.smtp.dev · read 15 Oct 2026
- Deliverability audit
- Its audit checks sender configuration, subject, HTML structure, links, images, and content patterns associated with spam filtering.smtp.dev · read 15 Oct 2026
- 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.smtp.dev · read 15 Oct 2026
- Domains and aliases
- Users can bring custom domains and subdomains, use catch-all accounts, and route plus-sign aliases.smtp.dev · read 3 Oct 2026
- 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.smtp.dev · read 15 Oct 2026
- Independent article date
- SMTPedia published its smtp.dev assessment on 11 July 2026.smtpedia.com · read 15 Oct 2026
- Independent classification
- SMTPedia classifies smtp.dev as a throwaway email provider and says it had tracked 361 rotating domains since approximately 2021.smtpedia.com · read 15 Oct 2026
- Independent criticism: abuse patterns
- SMTPedia claims smtp.dev addresses appear in free-tier abuse, referral farming, crypto-airdrop sybil activity, and chargeback-fraud patterns.smtpedia.com · read 15 Oct 2026
- 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.smtpedia.com · read 15 Oct 2026
