Is firstmailer.net valid?
How to block firstmailer.net e-mail domain
firstmailer.net
firstmailer.net is a domain that should be blocked from sign-ups or registrations. Based on our analysis, you should block this domain. If a user is trying to sign-up using an e-mail on this domain, it's likely that it's a malicious or fraudulent attempt for some reason.
The best way to detect and block domains like firstmailer.net is to use the Check-Mail API, available for free, for all programming languages.
Raw API JSON response:
"valid": true,
"block": true,
"disposable": false,
"email_forwarder": false,
"domain": "firstmailer.net",
"text": "Looks somewhat suspicious",
"reason": "Heuristics: T1",
"risk": 55,
"mx_host": "mx.plingest.com",
"possible_typo": [],
"mx_ip": "38.143.66.193",
"mx_info": "Using MX pointer mx.plingest.com from DNS with priority: 10",
"last_changed_at": "2025-06-04T09:51:59+02:00"
}
firstmailer.net
Status: Looks somewhat suspicious
RISK
MEDIUM
Domain risk: 55
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