SMTP Labs

Free plan APIWeb

What SMTP Labs is

SMTP Labs is an email testing service for capturing test messages in a sandbox and examining them through a web interface, IMAP, POP3, or API. Because the sandbox does not deliver mail to external recipients, it is intended for testing rather than sending to real inboxes. Inspect message text and HTML, headers, MIME structure, raw source, and attachments. SPF, DKIM, and DMARC checks are available in the interface and API, alongside an audit of sender setup, message markup, links, and content patterns flagged by spam filters. The REST API manages domains, accounts, mailboxes, messages, and tokens, and server-sent events can report new messages. SMTP, IMAP, and POP3 work without a vendor SDK. Teams can use standard SMTP and the REST API in GitHub Actions, Jenkins, GitLab CI, or CircleCI. Plans include free Lite with one domain, 50 accounts, and seven-day retention; Pro is $7 a month and Max is $20 a month. Retention varies by plan, up to 90 days.

Who it suits

It suits developers and teams checking email output and deliverability before release, including teams that run tests in CI. It is not for sending test messages to external recipients.

What it does well

Inspect HTML, text, headers, MIME, source, and attachments
SPF, DKIM, and DMARC checks in UI and API
REST API and server-sent event message updates
Works with SMTP, IMAP, and POP3 without vendor SDK
Free Lite plan includes one domain and 50 accounts

What to know first

Sandbox messages cannot reach external recipients
Full account deletion is unavailable
Retention depends on plan
Support obligations may be limited to paid subscriptions

Limits

Lite costs nothing and includes one domain, 50 accounts and seven-day message retention. Pro costs $7 a month and includes five domains, 25,000 accounts and 30-day retention; Max costs $20 a month and includes unlimited domains and accounts with 90-day retention.

Plans

Plan	Billed and limits	Price
Lite	monthly · 1 domain · 50 accounts · 7-day message retention · SMTP, IMAP, POP3, API · email audit	Free
Max	monthly · Unlimited domains · unlimited accounts · 90-day message retention · SMTP, IMAP, POP3, API · email audit · catch-all and aliasing	$20 a month
Pro	monthly · 5 domains · 25,000 accounts · 30-day message retention · SMTP, IMAP, POP3, API · email audit · catch-all and aliasing	$7 a month

As smtp.dev lists them, read 15 Oct 2026. The maker's own page has the final word.

Getting started

Visit smtp.dev
Choose Lite, Pro or Max
Send test email to the service over SMTP
Inspect messages through the web UI, IMAP, POP3 or API
For CI use, follow the maker’s documented setup for GitHub Actions, Jenkins, GitLab CI or CircleCI

Verdict

SMTP Labs brings message inspection, authentication checks, and deliverability auditing into a sandbox with API and protocol access. Check its retention limits and support terms against your workflow before choosing a plan.

Questions

Is there a free plan?

Yes. Lite costs nothing and includes one domain, 50 accounts and seven-day message retention.

What do the paid plans cost?

Pro costs $7 a month. Max costs $20 a month.

Which protocols and platforms are supported?

SMTP Labs is available on the web and through an API. It supports SMTP, IMAP and POP3 without requiring a vendor SDK.

Can its test emails be delivered to external recipients?

No. Email stays within the sandbox and cannot reach external recipients.

Where is account and email information stored and processed?

The privacy policy says it is primarily stored and processed in the United States.

Can users delete their accounts?

Users can request account deactivation, but full account deletion is unavailable because of anti-abuse obligations.

Facts from SMTP Labs's own pages

Account deletion: Users can request account deactivation, but full account deletion is unavailable because of anti-abuse obligations. · smtp.dev, 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, 3 Oct 2026
API authentication: API requests use an X-API-KEY header, and newly created token values are shown only once. · smtp.dev, 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, 15 Oct 2026
Authentication checks: Every received message can show SPF, DKIM, and DMARC verification results in the interface and API. · smtp.dev, 15 Oct 2026
Catch-all accounts: A wildcard account can capture mail for otherwise uncreated addresses on a domain. · smtp.dev, 15 Oct 2026
CI integrations: Documentation provides examples for GitHub Actions, Jenkins, GitLab CI, and CircleCI using SMTP plus the REST API. · smtp.dev, 15 Oct 2026
Client compatibility: Thunderbird and Apple Mail can connect over IMAP, while webmail is available at webmail.smtp.dev. · smtp.dev, 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, 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, 15 Oct 2026
Deliverability audit: Its audit checks sender configuration, subject, HTML structure, links, images, and content patterns associated with spam filtering. · smtp.dev, 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, 15 Oct 2026
Domains and aliases: Users can bring custom domains and subdomains, use catch-all accounts, and route plus-sign aliases. · smtp.dev, 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, 15 Oct 2026
Independent article date: SMTPedia published its smtp.dev assessment on 11 July 2026. · smtpedia.com, 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, 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, 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, 15 Oct 2026
Independent DNS finding: DNSCheck.pro observed Cloudflare authoritative nameservers and an MX record pointing to mx.yandex.net for smtp.dev. · dnscheck.pro, 15 Oct 2026
Independent DNS limit: DNSCheck.pro reported that smtp.dev lacked a DMARC record at the time of its September 2025 scan. · dnscheck.pro, 15 Oct 2026
Independent DNS report date: DNSCheck.pro's report for smtp.dev was generated on 25 September 2025. · dnscheck.pro, 15 Oct 2026
Independent mail test: DNSCheck.pro's scan found the domain's mail server rejected [email protected] but accepted [email protected]. · dnscheck.pro, 15 Oct 2026
Integrations: The maker documents CI use with GitHub Actions, Jenkins, GitLab CI, and CircleCI, using standard SMTP and the REST API. · smtp.dev, 3 Oct 2026
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. · smtp.dev, 15 Oct 2026

Where SMTP Labs stands on Freedom251

Email Testing Software#17 of 28