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A developer’s free email verification API advertises 100 calls per day and checks address format and domain mail-routing records. Those checks can help catch malformed addresses or domains without mail routing, but they do not prove that a specific mailbox exists or that its owner controls it. The figures and feature list come from the project author, not an independent test.
What the project says the API does
In a DEV Community post published September 27, 2026, project author Aimly writes: “I built a simple email verification API using FastAPI + Python.” The post lists RFC 5322 format validation, MX record checking, a REST API, 100 free calls per day, and a 10 ms response time. These are the author’s claims; the response-time figure is not an independently measured benchmark, and the stated free allowance has not been confirmed as the current enforced limit. Read the project post.
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The linked repository was not successfully inspected and the live demo was not tested. The available information does not establish the current service’s API route, request or response format, authentication, error behavior, privacy practices, data retention, uptime, or deployment region. It also does not say whether the daily limit applies per key, IP address, user, or across the service.
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Address-format validation
A syntax check looks at whether an input resembles an email address under the rules the implementation applies. The post describes its check as RFC 5322 validation, but the code and tests were not available for review, so it is not established that the parser supports the full range of valid address forms. A syntax result is not a check that the address can receive mail.
#1 Best Overall
Domain mail-routing checks
SMTP uses DNS to find where mail for a domain should be delivered. RFC 5321 describes looking up MX records and, when no MX record exists, falling back to the domain’s address records. That lookup concerns routing for the domain; it does not show that an individual mailbox exists, is accepting messages, or belongs to the person who entered it. RFC 5321: Simple Mail Transfer Protocol.
A domain can also publish a Null MX record to say explicitly that it does not accept email. RFC 7505 defines this signal. A useful implementation should distinguish that deliberate configuration from a DNS lookup failure or timeout; the project post does not establish how this API handles those cases. RFC 7505: A Null MX DNS Resource Record for Domains That Do Not Accept Email.
Rank #2
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Does checking MX records verify an email address?
No—not by itself. An MX lookup can indicate that a domain publishes mail-routing information, but it cannot confirm a particular mailbox or prove control of it. DNS errors and timeouts also should not automatically be treated as definitive evidence that an address is invalid. The project’s public post does not document its error handling, nor does it claim to send a confirmation message or otherwise verify mailbox ownership.
Which kind of check fits your goal?
| Approach | What it observes | What it does not establish |
|---|---|---|
| Syntax-only validation | Whether an input passes the address-format rules used by the validator | Whether the domain routes mail or the mailbox exists |
| Domain-routing check | DNS mail-routing data, such as MX records; SMTP routing can also use address-record fallback when there is no MX record, as RFC 5321 describes | Whether a particular mailbox exists, accepts mail, or is controlled by the submitter |
| Confirmation sent to the address | Whether someone with access to the inbox can complete the confirmation flow | Future deliverability or permanent ownership |
For basic input hygiene, a format check can catch obvious mistakes before saving a form. A routing check adds domain-level information, but should expose uncertainty rather than collapsing timeouts and DNS failures into a simple “invalid” result. If your requirement is to establish that a user can access an address, use a confirmation flow; the project post does not say that this API provides one.
Rank #3
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What to check before relying on this API
- Confirm the live endpoint, request and response schema, and authentication method from current project documentation.
- Check whether the stated 100-call daily allowance is still available and how it is counted. The post does not specify whether it is per key, per IP, per user, or global.
- Look for distinct outcomes for a missing MX record, Null MX, DNS failure, and timeout; do not assume the service handles them correctly based on a reader comment.
- Review what input data is logged or retained and whether the service’s privacy terms suit the addresses you plan to submit.
- Test behavior against addresses and domains relevant to your application before making the API a production dependency.
If your use case needs support commitments, documented privacy terms, predictable limits, or higher-volume processing, a hosted email-verification service may be a better operational fit. The project’s stated free allowance alone does not establish those guarantees.
Quick Recap
Best Value
- The latest SonicWall TZ370 series, are the first desktop form factor nextgeneration firewalls (NGFW) with 10 or 5 Gigabit Ethernet interfaces. The series consist of a wide range of products to suit a variety of use cases.
- Reduce complexity and get the business running without relying on IT personnel with easy onboarding using SonicExpress App and Zero-Touch Deployment, and easy management through a single pane of glass
- Drive business growth by investing in next-gen appliances with multi-gigabit and advanced security features, to future-proof against the changing network and security landscape.
- SonicWall 8x5 Support provides chat, email, web, and telephone support for technical assistance | Dynamic Support is designed for customers who need continued protection through ongoing firmware updates and advanced technical support
- Hardware: Operating system: SonicOS 7.0 | Interfaces: 8x1GbE, 2 USB 3.0, 1 Console | Management: Network Security Manager, CLI, SSH, Web UI, GMS, REST APIs | VLAN Interfaces: 128 | Access points supported (maximum): 20
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