These services specialize in verifying if a number is a valid fax line.
Experian Data Quality — Offers phone/fax verification with bulk processing.
Melissa Data — Phone and fax number fax lists verification, plus append services.
TLOxp (TransUnion) — Comprehensive phone validation, including fax.
DataValidation — Bulk phone/fax verification API.
2. General Phone Verification Tools
Since fax numbers are a type of phone number, these tools help verify if the number is active and formatted correctly.
NumVerify — API-based phone number validation (can detect fax line status).
Twilio Lookup — Can identify line type (mobile, landline, fax) via API.
PhoneValidator.com — Bulk phone number validation with line type detection.
3. Custom Fax Test Sending
Use fax broadcast software (e.g., FaxLogic, SRFax) to send small batches of test faxes.
Track bounce rates, busy signals, and no-answers to identify invalid numbers.
4. Data Cleaning Platforms
OpenRefine — Helps detect formatting errors, duplicates, and inconsistencies.
Dedupe.io — For fuzzy matching and deduplication (can improve list quality before verification).
Tips for Effective Fax List Verification
Combine multiple tools: Use phone validation to weed out inactive numbers, then a fax-specific validator for line type confirmation.
Regularly verify: Fax numbers can change; schedule verification quarterly or before major campaigns.
Integrate APIs: Automate verification with your CRM or fax marketing platform for real-time list hygiene.
Final ThoughtUsing bulk fax list verification tools saves you money, improves delivery rates, and keeps you compliant. It’s a must-have step before any serious fax marketing effort.
Want help setting up automated fax number verification or recommendations tailored to your database size?