Valid format doesn't mean reachable: 2 checks teams skip before paying to send

If you run SMS, WhatsApp, or dialer campaigns from imported lists, you have seen this: the CSV passes a basic "valid format" check, still 20-40% of sends fail or never reach a handset.

The confusion is that "valid" answers different questions:

1.

Format (E.164 syntax)

- is the string a phone number with a correct country code? This kills junk rows and missing-code rows first. Cheap and fast, but it says nothing about whether the number can receive anything.

2.

Duplicates

- same contact 2-3 times in one file, or across broker files. If you pay per record, duplicates are pure waste. Always dedupe and normalize (E.164) before you pay for deeper checks.

3.

Line type

- mobile vs landline vs VoIP vs premium. SMS and WhatsApp are only possible on mobile (and some VoIP). Routing a landline to a mobile-only campaign guarantees failure.

4.

Carrier / MNP

- which carrier actually serves the number today? Numbers port between carriers (MNP), so old carrier data mis-routes and mis-segments.

5.

Registration / reachability signal

- is the number live on WhatsApp, Telegram, iMessage, or RCS? A valid mobile can be completely unregistered on the channel you planned to use. This is a different signal from line type.

Practical preflight most teams can run this week: take a 500-1000 row sample, run format + dedupe first, then line-type, then a registration check for your target channel. If 15-20% fails the first two steps, the rest of the file will not be better - useful signal before you negotiate with a broker or pay for full processing.

Example: a 50k file where 6k are malformed/duplicates, 7k are landline/VoIP when you needed mobiles, and 9k are not WhatsApp-registered when WhatsApp was your plan - that is 22k records (44%) you would have paid to process or try to message. Catching them before you route changes the economics.

If you are cleaning or verifying phone/email datasets before outreach, you can check the verification workflows at

https://phoneveriflo.com

- but the habit matters more than the tool: verify before you send, import, route, or pay.

How do you handle broker lists that look clean in Excel but waste budget after send - refund, re-process, or walk away?