Validating phone numbers for a Portugal list is crucial for ensuring deliverability, reducing costs, and maintaining compliance. Several techniques are employed, often used in combination for best results:
Format Validation: This is the initial check. Portuguese phone numbers typically follow specific formats. Mobile numbers usually start with 9, followed by 7 more digits (e.g., 9x xx xx xx xx). Landlines often start with 2, 28, or 21, followed by 7 or 8 digits (e.g., 21x xx xx xx or 28x xx xx xx). The validation checks if the number adheres to one of these standard patterns, including the correct number of digits (usually 9 digits, or 10 including the leading '9' for mobiles). It also checks for the presence of invalid characters.
Check Digit Verification (Luhn Algorithm): While not universally applied to all Portuguese numbers like in some other countries, certain specific identifiers or formats might incorporate a check digit. The Luhn portugal phone number list algorithm is a common formula used to validate a variety of identification numbers. If applicable, this algorithm verifies the integrity of the number by checking the calculated check digit against the provided one.
Network Validation (HLR Lookup - Optional but Powerful): This more advanced technique involves querying the Home Location Register (HLR) of mobile networks. An HLR lookup can confirm if the number is active on a specific carrier's network, whether the device is roaming, or if the number has been disconnected or ported. This provides a high degree of certainty about the number's validity and status but is typically more expensive and slower than other methods.
Presence in Do Not Call Lists: Crucially, validation also involves checking if the number is registered on Portugal's official Do Not Call (DNCL) list, the "Lista de Opposição à Telemarketing" (LPT) managed by ETEN (Entidade de Transparência do Emprego). Validating against this list is essential for compliance with Portuguese telemarketing regulations (DL 24/2012).
Combining these techniques helps create a clean, compliant, and effective Portugal phone number list.