Email Validation Explained
How Trust Leads validates email addresses using MX lookup, disposable detection, typo suggestions, and suspicious TLD checks.
Syntax Validation
The first step in email validation is checking whether the address conforms to the RFC 5321/5322 email syntax standard. This catches obvious errors like missing @ signs, double dots, invalid characters, and domain names that fail DNS naming rules.
Syntax validation is near-instant and does not require a network call. It produces the email_valid field in your output. An address can be syntactically valid but still undeliverable — that is why Trust Leads goes further with MX record lookup and domain checks.
MX Record Lookup
After syntax validation passes, Trust Leads performs a DNS MX (Mail Exchanger) record lookup for the email's domain. MX records tell the internet which servers accept email for a given domain. If a domain has no MX records, email sent to any address on that domain will bounce immediately.
The result is stored in the email_mx_found column. A value of 'false' means the domain either does not exist in DNS, has no MX records configured, or is temporarily unreachable. Around 8–12% of B2B contact lists have domains with missing MX records — usually because the company has rebranded, been acquired, or shut down.
- email_mx_found: true — domain has valid MX records, email can be delivered
- email_mx_found: false — domain has no MX records; email will bounce
- This does not confirm the specific mailbox exists — only that the domain accepts mail
Tip
If email_mx_found is false but you are confident the company still exists, check whether they have recently migrated email providers or rebranded. A manual Google search of the company domain is often the fastest way to confirm.
Disposable Email Detection
Disposable (or temporary) email services like Mailinator, Guerrilla Mail, and 10 Minute Mail allow anyone to create throwaway addresses that expire after minutes or hours. Contacts using disposable addresses almost never represent real business leads.
Trust Leads maintains an actively-managed blocklist of 250+ disposable email domains. This list is updated weekly as new disposable services emerge. If an email address uses a domain on this list, the email_disposable field is set to 'true' and the lead score is heavily penalised.
Warning
Sending email campaigns to disposable addresses is a significant sender reputation risk. Even if the address temporarily exists, the recipient has no intent to engage. Filter out all records where email_disposable is true before any outreach.
Domain Typo Detection
Typos in email domains are extremely common in manually entered data. 'gmial.com' instead of 'gmail.com', 'yahooo.com' instead of 'yahoo.com', or 'hotmali.com' instead of 'hotmail.com' account for a significant share of invalid contacts in typical B2B datasets.
Our typo detection engine uses a combination of edit-distance algorithms and a curated dictionary of the 500 most common email providers globally. When a close match is found, the corrected domain is written to the email_domain_suggestion column (e.g. 'gmail.com'). The original email address is preserved in the email column — we never silently modify your data.
# Example output columns for a row with email "john@gmial.com"
email = john@gmial.com
email_valid = false
email_mx_found = false
email_disposable = false
email_domain_suggestion = gmail.com
lead_score = 22
enrichment_flags = DOMAIN_TYPO|NO_MX_RECORDSuspicious TLD Detection
Certain top-level domains (TLDs) are disproportionately associated with spam, fraud, and low-quality signups. Trust Leads flags email addresses on high-risk TLDs including .xyz, .top, .click, .men, .loan, .download, .stream, and others from ICANN's new gTLD program that have become common in spam networks.
A suspicious TLD flag does not mean the email is invalid — legitimate businesses do occasionally use non-traditional TLDs. However, it is a signal worth reviewing manually before committing to outreach. The flag appears as SUSPICIOUS_TLD in the enrichment_flags column and contributes a moderate negative adjustment to the lead score.
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