Why do e-commerce SMS campaigns have high undeliverable rates?

Three causes account for most undeliverable SMS in e-commerce: landline numbers (which cannot receive any SMS), invalid numbers that have been disconnected or were never real, and VOIP numbers from providers that block commercial SMS. Customers often enter a phone number at checkout without thinking about whether it is their mobile number. Home lines and work numbers end up in customer databases regularly.

How do I clean my Klaviyo or Postscript subscriber list?

Export your subscriber list from Klaviyo, Postscript, or any SMS platform as a CSV. The export will include phone numbers plus profile data. Upload the CSV to PhoneCheckr, which adds a Type column (mobile, landline, voip, invalid) and a Carrier column to each row. Filter out landline and invalid rows, then re-import the cleaned mobile-only segment into your SMS platform as a new list or update the existing profiles.

Does phone validation help with SMS compliance?

Phone validation is a technical check. It tells you whether a number is valid and what type it is. It does not replace consent compliance under TCPA or CTIA guidelines. You still need proper opt-in records for every contact you text. What validation does is prevent wasted spend and carrier flags from sending to numbers that can never receive your messages.

How often should I validate my SMS subscriber list?

For most e-commerce brands, a quarterly validation pass is enough. Numbers go invalid when customers change phones, switch carriers, or cancel service. A list that was clean six months ago will have some decay. Run a validation pass before major campaign periods (Black Friday, holiday season, back-to-school) to ensure you are working with fresh data.

Can phone validation reduce SMS costs?

Yes, directly. SMS platforms charge per send attempt, not per delivery. Every message you send to a landline or invalid number is a wasted send. On a list with 15% bad numbers, validating before a campaign reduces your send volume, and therefore your cost, by 15%, while improving your deliverability rate and sender reputation.

What is the difference between SMS validation and email validation?

Email validation checks whether an email address exists and has an active mailbox. Phone validation checks whether a phone number is currently assigned to a carrier, what type it is, and which carrier holds it. Both reduce waste and improve deliverability, but they operate on different data. For an e-commerce brand running both email and SMS channels, validating both contact types before campaigns is standard practice.

Phone number validation for e-commerce: stop paying to send to numbers that can't receive SMS

Every landline and invalid number in your subscriber list is a wasted send. Validate your list before campaigns to cut costs and protect your sender reputation.

Upload a CSV and validate your phone list

No account required · Results in under 60 seconds

What bad phone numbers cost an e-commerce SMS program

E-commerce customer databases accumulate bad phone numbers over time. Customers enter home landlines at checkout. Numbers get disconnected when people switch carriers. VOIP numbers from apps like Google Voice end up in your list alongside real mobile numbers. None of these contacts will ever receive your SMS, but you pay to send to all of them.

10–20%

typical bad number rate in an unvalidated e-commerce SMS list

$0.01

average SMS platform cost per send attempt, including undeliverables

$100

wasted spend per 10,000 sends on a list with 10% bad numbers

Watch out

High undeliverable rates get your sending number flagged by carriers. Once flagged, deliverability drops on your good contacts too, not just the bad ones.

Where e-commerce brands use phone validation

1
Abandoned cart sequences. Your abandoned cart SMS is one of the highest-ROI messages you send. Sending it to a landline or disconnected number wastes that opportunity and the send cost. Validate your subscriber list quarterly to keep abandoned cart flows hitting real mobile numbers.
2
Pre-campaign list cleaning. Before Black Friday, holiday campaigns, or any high-volume send, run your full list through PhoneCheckr. The cost of validation (typically $10–$50 for most lists) is a fraction of the wasted spend on a dirty list.
3
Checkout phone field cleanup. If your store has been collecting phone numbers at checkout for years, a significant portion of older records are likely stale. A one-time validation pass on your full customer database removes the dead weight before you migrate to a new SMS platform or reactivation campaign.
4
Lead scoring and segmentation. Line type is a signal for contact quality. A mobile number from a major carrier is a stronger contact than a VOIP number from a forwarding service. You can use line type data to prioritize high-value contacts in winback campaigns and re-engagement flows.

How to validate your SMS list before a campaign

1
Export your subscriber list. From Klaviyo, Postscript, Attentive, or your ESP, export subscribers with phone numbers as a CSV. Include any profile data you want preserved (name, email, segment tags) so you can reimport the full record after validation.
2
Upload to PhoneCheckr. Drop the file onto the upload area. PhoneCheckr finds the phone number column and processes every row. A list of 10,000 contacts typically finishes in two to three minutes.
3
Download the enriched CSV. Each row now has a Type column (mobile, landline, voip, invalid) and a Carrier column. Open in Excel or Google Sheets.
4
Filter and reimport. Delete invalid rows. Move landline rows to a voice-only list. Keep mobile rows for your SMS campaigns. Reimport to your SMS platform, or use the filtered CSV to suppress bad numbers from your next send.

Validation costs $0.01 per number. Start cleaning your list here.

Common questions about e-commerce SMS validation

Why do e-commerce SMS campaigns have high undeliverable rates?
How do I clean my Klaviyo or Postscript subscriber list?
Does phone validation help with SMS compliance?
How often should I validate my SMS subscriber list?
Can phone validation reduce SMS costs?
What is the difference between SMS validation and email validation?

Clean your list before the next campaign. upload a CSV and clean your list. Also see: how to clean an SMS list · phone validation for real estate