SMTP Labs

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Score6.9

Rank#6 of 28

From$7/mo

Free planYes

Runs onAPI, Web

Summary

SMTP Labs is an email testing service for receiving test messages and inspecting them in a web interface, through IMAP or POP3, or with its API. Messages remain inside its sandbox, so they cannot reach external recipients. Users can examine HTML and plain text, headers, MIME structure, raw source, and attachments. The interface and API show SPF, DKIM, and DMARC checks, and a deliverability audit reviews sender settings, HTML structure, links, and content patterns that spam filters flag. Its REST API covers domains, accounts, mailboxes, messages, and tokens; server-sent events can push new messages as they arrive. SMTP, IMAP, and POP3 do not require a vendor SDK. The free Lite plan includes one domain, 50 accounts, and seven-day message retention. Pro costs 7.00 USD per month and Max costs 20.00 USD per month. Retention varies by plan, up to 90 days. Email and account information are primarily stored and processed in the United States.

Who it is for

SMTP Labs suits developers and teams who need to inspect test email without sending it to external recipients. Its documented CI integrations include GitHub Actions, Jenkins, GitLab CI, and CircleCI.

What is good

Inspect messages through web, IMAP, POP3, or API.
Checks SPF, DKIM, and DMARC.
Supports custom domains, catch-all accounts, and plus aliases.
New messages can be pushed through server-sent events.

What to know first

Sandbox messages cannot reach external recipients.
Lite retains messages for seven days.
Full account deletion is unavailable.
Support is not guaranteed except as included in paid plans.

Verdict

SMTP Labs provides multiple ways to inspect test messages and check authentication and deliverability. Consider its retention limits, sandbox restriction, and account-deletion policy before adopting it.

SMTP Labs plans and pricing

All plans

Lite Free 1 domain · 50 accounts · Messages kept for 7 days · SMTP, IMAP, POP3, API · Email audit smtp.dev · 3 Oct 2026

Pro $7/mo 5 domains · 25,000 accounts · Messages kept for 30 days · SMTP, IMAP, POP3, API · Email audit · Catch-all & aliasing smtp.dev · 3 Oct 2026

Max $20/mo Unlimited domains · Unlimited accounts · Messages kept for 90 days · SMTP, IMAP, POP3, API · Email audit · Catch-all & aliasing smtp.dev · 3 Oct 2026

Compared on email testing software

Free plan: Yessmtp.dev
Paid from: $7/mosmtp.dev
Spam checks: Yessmtp.dev
Link checks: Yessmtp.dev
Inbox testing: Yessmtp.dev
API access: Yessmtp.dev

Facts

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.smtp.dev · 3 Oct 2026
Sandbox: The service receives real email but sends only within its sandbox, so test messages cannot reach external recipients.smtp.dev · 3 Oct 2026
Protocols: The product supports SMTP, IMAP, and POP3 without requiring a vendor SDK.smtp.dev · 3 Oct 2026
Message inspection: Users can inspect HTML and plain text, headers, MIME structure, raw source, and attachments.smtp.dev · 3 Oct 2026
Authentication checks: SPF, DKIM, and DMARC checks are shown in the UI and available through the API.smtp.dev · 3 Oct 2026
Deliverability audit: The deliverability audit reviews sender configuration, HTML structure, links, and content patterns spam filters flag, grouped by severity.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
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
Domains and aliases: Users can bring custom domains and subdomains, use catch-all accounts, and route plus-sign aliases.smtp.dev · 3 Oct 2026
Retention: Message retention depends on the plan and can be up to 90 days, with shorter per-message expiry available.smtp.dev · 3 Oct 2026
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.smtp.dev · 3 Oct 2026
Data location: The privacy policy says email content and account information are primarily stored and processed in the United States.smtp.dev · 3 Oct 2026
Account deletion: Users can request account deactivation, but full account deletion is unavailable because of anti-abuse obligations.smtp.dev · 3 Oct 2026
Support: The terms state the company has no support or maintenance obligation except as may be included in a paid subscription plan.smtp.dev · 3 Oct 2026