Reject emails from domains that cannot receive mail
VerifyWall performs DNS lookups to verify that an email's domain has valid MX records — filtering out fabricated domains that can't receive verification emails.
What it is
MX (Mail Exchange) records are DNS entries that specify which mail servers are responsible for receiving email for a domain. A domain without MX records cannot receive email. When someone signs up with an email from such a domain, they cannot receive verification emails, password resets, or any transactional communications.
Why it matters for SaaS
Emails from domains without MX records are guaranteed to bounce. Sending to them wastes your email delivery resources, hurts your sender reputation with email providers, and increases bounce rates that can lead to your domain being blacklisted. For SaaS platforms, these signups represent dead-end accounts that will never complete onboarding.
How VerifyWall detects it
VerifyWall performs real-time DNS queries to check for MX records on the email domain. We check both explicit MX records and fallback A/AAAA records (per RFC 5321, which allows mail delivery to the A record when no MX exists). Only domains with no mail delivery capability are flagged. The "no_mx_records" reason is added to the API response.
Risk score impact
No MX records detection adds 30 points to the risk score. This is a strong signal because legitimate email domains virtually always have MX records configured.
API response example
When this threat type is detected, the API returns a response like this:
{
"data": {
"id": "a1b2c3...",
"type": "checks",
"attributes": {
"subject": "[email protected]",
"subject_type": "email",
"risk_score": 30,
"risk_level": "low",
"reasons": [
"no_mx_records"
],
"details": {
"email": "[email protected]",
"domain": "fakebusiness123.xyz",
"is_disposable": false,
"has_mx_records": false,
"is_free_provider": false
}
}
}
}Frequently asked questions
What if a domain has A records but no MX records?
Per RFC 5321, email can be delivered to a domain's A record when no MX record exists. VerifyWall follows this standard — we only flag domains that have neither MX records nor A/AAAA records that could accept mail delivery.
Can newly registered domains trigger false positives?
Newly registered domains that have their MX records configured will not be flagged. Only domains that genuinely cannot receive email are detected. If a domain is newly registered but has proper DNS setup, it will pass this check.
How does this differ from disposable email detection?
Disposable email detection identifies known temporary email services that can receive email (they have MX records) but are designed for short-term use. No MX records detection identifies domains that cannot receive email at all — often randomly generated or typosquatted domains used by bots.
Related resources
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