Importing a CRM or dialer list? 5 checks to run before you route or pay
If you run a VoIP operation, wholesale route, or a dialer/sales team that imports contact lists into a CRM or softswitch, you have probably seen this: the CSV looks fine in Excel, then 20-40% of the numbers waste money or fail the moment you try to route, send, or dial.
Most 'is this number valid?' questions are actually five different checks - and each one catches a different kind of junk:
1. Format (E.164) - is the row even a dialable number with the right country code? Malformed rows fail before anything else and are free to drop.
2. Duplicates - is the same contact in the file twice? At per-record pricing or per-send cost, duplicates are pure waste.
3. Line type - mobile vs landline vs VoIP vs premium-rate. This decides whether SMS, WhatsApp, or voice are even possible for that row.
4. Carrier / MNP - which carrier serves the number TODAY? With number portability, a number can live on a different network than your old data says.
5. Reachability / registration - is the number actually registered on WhatsApp, Telegram, RCS or iMessage? A perfectly valid mobile number can be completely inactive on the channel you planned.
Cheap habit that pays for itself: normalize to E.164 and dedupe first, then run a preflight on a sample (say 500-1k rows) before you pay to verify the full file. If 15% of the sample fails format/dedupe and another 15% are VoIP/landline when you only wanted mobiles, the whole file is telling you something - fix the source before you commit the route or campaign.
Example: a 50k file where 10% are malformed, 8% duplicates, and 18% are landline/VoIP when you wanted mobiles - that's 18k records you don't need to pay to process or try to message. Catching them before processing changes the economics.
If you are cleaning phone/email data before outreach or before an import, you can review the bulk verification and preflight workflows at
- but the habit is more important than the tool: clean before you import, verify before you send.
Curious how others handle it - do you block bad lists at import, run a preflight, or just pay and filter after?
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