Mail.cx

Free plan APIWeb

What Mail.cx is

Mail.cx provides temporary inboxes for receiving email in developer workflows; it does not send messages. Developers, QA teams, and product teams can use it to check account verification, transactional messages, notification pipelines, and application integrations. A web inbox is available without signup, with a choice of username or a randomly generated one. Server-sent events can deliver new mail to the browser as it arrives. The REST API supports long-polling, retrieval of parsed or raw email, attachment downloads, and event delivery. It allows 10 requests per second per token; long-polling is limited to one concurrent wait per token and 10 per address. Mail is deleted automatically after one hour on Free and 72 hours on Pro. Free costs nothing; Pro is listed at $9.90 a year, while the pricing note also says paid from $4/mo. The service says connections use TLS, passwords are hashed with bcrypt, and API tokens are stored as SHA-256 hashes. Its terms say retention and recovery are not guaranteed and caution against using it for critical, sensitive, or business-essential communications.

Who it suits

Mail.cx suits developers, QA teams, and product teams checking incoming messages in tests and application workflows. It is not for sending email or for communications that must be retained or recovered.

What it does well

Web inbox available without signup
Supports parsed or raw email retrieval
API can download attachments
New messages can appear through server-sent events

What to know first

Cannot send email
Free mail is retained for only one hour
Message retention and recovery are not guaranteed
Not intended for critical or sensitive communications

Limits

Free mail is retained for one hour, and the Free plan is listed as a web inbox. Pro mail is retained for 72 hours before automatic deletion. API use is limited to 10 requests per second per token; long-polling is limited to one concurrent wait per token and 10 per address.

Plans

Plan	Billed and limits	Price
Free	real-time delivery · public system domains · 1-hour mail retention · no signup · rate-limited web inbox	Free
Pro	$9.9/year · 72-hour retention · up to 100 custom domains · dedicated system domains · up to 100 API keys · 10 requests/second · unlimited web inbox without free-plan limits	$9.90 a year

As mail.cx lists them, read 19 Oct 2026. The maker's own page has the final word.

Getting started

Open https://mail.cx/ in a browser for a web inbox.
Choose a username or generate one randomly; web inboxes do not require signup.
Use the REST API for inbox access, message retrieval, attachments, or event delivery.
Choose Pro for API access, custom domains, dedicated system domains, and 72-hour retention.

Verdict

Mail.cx provides temporary receiving inboxes and API tools for email testing. Its short retention and no-send design make it unsuitable for messages that need dependable storage or delivery.

Questions

Is Mail.cx free?

Yes. The Free plan is listed as free. The pricing note says Free plan · paid from $4/mo, while Pro is listed at $9.90 a year.

Does Mail.cx send email?

No. Mail.cx receives email and does not provide email sending functionality.

Which platforms does Mail.cx support?

The listed platforms are web and API.

How long are messages retained?

Mail is kept for one hour on Free and 72 hours on Pro, then automatically deleted.

Who operates Mail.cx?

Mail.cx is operated by SICHUAN HAONI E-COMMERCE CO., LTD.

Can I use a custom domain?

The API documentation describes adding a custom domain using DNS verification records. The Pro plan lists custom domains.

Facts from Mail.cx's own pages

Advertising boundary: The inbox, message-reading view, dashboard and authentication screens do not load advertising scripts, while selected marketing pages may show Google AdSense. · mail.cx, 19 Oct 2026
API: The REST API supports long-polling inboxes, retrieving parsed or raw email, downloading attachments, and server-sent event delivery. · mail.cx, 29 Sept 2026
API attachments: Individual email attachments can be downloaded by zero-based attachment index. · mail.cx, 19 Oct 2026
API base: The REST API uses https://api.mail.cx/v1 and authenticates with an x-api-token header. · mail.cx, 19 Oct 2026
API domain management: API endpoints allow adding, listing and deleting custom domains and checking verification status. · mail.cx, 19 Oct 2026
API hold time: Long-poll requests remain open for a server-fixed maximum of 25 seconds. · mail.cx, 19 Oct 2026
API inbox endpoint: The API supports long-polling inbox retrieval with cursor-based since parameters. · mail.cx, 19 Oct 2026
API limits: The API allows 10 requests per second per token; long-polling is limited to one concurrent wait per token and 10 per address. · mail.cx, 29 Sept 2026
API message formats: Developers can retrieve parsed text, HTML and attachments or download the original .eml stream. · mail.cx, 19 Oct 2026
API rate limits: Pro API tokens are limited to 10 requests per second, one concurrent long-poll per token and ten per address. · mail.cx, 19 Oct 2026
API SSE: The API offers server-sent event endpoints for one address or all owned addresses. · mail.cx, 19 Oct 2026
API token management: Tokens can be created, listed and revoked through API endpoints, with plaintext shown only at creation. · mail.cx, 19 Oct 2026
Automatic deletion: Messages and inbox data are automatically deleted when the applicable retention period ends. · mail.cx, 19 Oct 2026
Custom domains: Pro users can connect up to 100 custom domains using DNS verification. · mail.cx, 19 Oct 2026
Custom usernames: Users may choose their own local part or have one generated randomly. · mail.cx, 19 Oct 2026
Dedicated domains: The Pro plan includes dedicated system domains in addition to public domains. · mail.cx, 19 Oct 2026
External associated-domain count: Check-Mail reports fewer than 100 domains associated with mail.cx and says the newest was added five days earlier when checked. · check-mail.org, 19 Oct 2026
External classification: Check-Mail classifies mail.cx as a temporary-email provider and recommends blocking associated domains at signup to prevent abuse. · check-mail.org, 19 Oct 2026
External detection: Check-Mail says its API detects and blocks mail.cx domains in real time, including newly appearing domains. · check-mail.org, 19 Oct 2026
External domain age: HypeStat reported that the mail.cx domain was created on January 29, 2016 and registered through CentralNic. · hypestat.com, 19 Oct 2026
External hosting: HypeStat resolved mail.cx through Cloudflare IP addresses and ASN AS13335. · hypestat.com, 19 Oct 2026
External HTTPS status: HypeStat reported that mail.cx supports HTTPS and has a certificate for *.mail.cx. · hypestat.com, 19 Oct 2026
External technology detection: HypeStat detected Cloudflare, Google AdSense and HTTP/3 on mail.cx. · hypestat.com, 19 Oct 2026
External traffic estimate: HypeStat estimated about 124 daily visitors and 170 daily page impressions for mail.cx. · hypestat.com, 19 Oct 2026

Where Mail.cx stands on Freedom251

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