Before You Text 40,000 People: The SMS Pre-Flight Checklist for Event and Webinar Reminders

Key takeaways

• Stop before a big send and work through ten checks. Every one maps to a failure we've seen on a live event or webinar.
• Validate and dedupe first. In our experience, a list texted for years without validation keeps only about 40–45% of its raw records as unique, SMS-capable numbers.
• Validating 40,000 numbers by line type costs $320 at Twilio's list price.[1] One bad batch can stop every text on a HighLevel account until 00:00 UTC.[2]
• Count the segments in the final copy. One curly quote or emoji drops a text from 160 characters per segment to 70, which can double the bill.[3]
• Send by the recipient's clock, not yours. Florida, Oklahoma and Maryland stop at 8 p.m.[4][5][6]
• Drip the send under your daily cap, keep raw links out of the first text, and have the same message ready by email.

Before you text a big list, stop and work out everything that can go wrong. That pause is the checklist: validate line type, check for reassigned numbers, confirm consent, put the number on the registered campaign, seed-test, drip under your cap, respect the send window, keep raw links out of the first text, price the segments and international numbers, and line up backup email.

Each item maps to a failure we've seen. Run all ten and our target is 95% or better delivered on the send. We haven't found an industry delivery benchmark with a disclosed method to compare it to, so treat that as the number we hold ourselves to.

The pre-send pause

Big sends fail in the same few ways: dead numbers, an unregistered number, a burst that trips the account's limits, a filtered link, a send that lands at 6 a.m. Most are visible in advance if someone looks.

So before any send to an old or imported list, one person owns a 30-minute pause and works the list below. It's the cheapest step in the launch.

The 10-point pre-flight checklist

1. Validate line type

Run every number through a line-type lookup and drop landlines and invalid numbers. Twilio's Line Type Intelligence returns 12 types, from mobile and landline to fixed and non-fixed VoIP, toll-free and pager.[7] It costs $0.008 a lookup.[1] Texts to a landline fail with error 30006, and Twilio's advice is to look the number up first and not retry.[8]

Older audiences carry more landlines. In CDC survey data for the second half of 2024, 4.3% of adults 65 and over lived landline-only, against 1.4% of all adults.[9] Lists pick up landlines mostly from people typing a home or office number into a form.

Telnyx charges $0.0015 for an LRN query, but that returns carrier routing, not line type, so it isn't a like-for-like substitute.[10]

2. Dedupe and check reassigned numbers

Dedupe before you validate, so you don't pay twice for the same number. On the lists we audit, duplicates sharing one number are a big share of what disappears.

Then check for reassigned numbers on anything aged. The FCC estimated in 2018 that about 35 million US numbers are disconnected and made available for reassignment each year.[11] Its rule gives a safe harbor if you had consent and the FCC's Reassigned Numbers Database wrongly reported the number as not disconnected, and only that database qualifies.[12] Queries cost $0.008 each at Tier 1 and $0.006 at Tier 2.[13] CTIA also expects senders to process deactivation files regularly and remove those numbers.[14]

In our experience, on a list texted for years without validation, only about 40–45% of raw contact records end up as unique, SMS-capable numbers after dedupe and line-type checks. No public industry figure exists to compare it to. Our phone verification statistics collect the primary-sourced numbers that do exist.

3. Confirm where consent came from

Know the source of every number before it gets a marketing text. The FCC's rule requires prior express written consent for autodialed marketing texts: a signed agreement, where an E-SIGN electronic signature counts, that says consent isn't a condition of purchase.[12] CTIA says consent doesn't transfer between campaigns and that rented, sold or shared lists shouldn't be texted.[14] The FCC has also codified that National Do Not Call Registry protections apply to texts.[15]

Imported lists from a previous operator are where this breaks. If nobody can say how a segment opted in, don't text it. Registration, consent and verification explains what evidence to keep.

4. Put the sending number on the registered campaign

Twilio blocks US texts from 10-digit numbers that aren't on an approved A2P campaign (error 30034).[16] Every new number has to be attached to the campaign after you buy it.[17] We've seen a fresh number bought for a workflow that nobody added to the campaign.

A new number for a new job is fine. Dropping numbers as they degrade to dodge filters is number cycling, which T-Mobile's Code of Conduct prohibits.[18] Our A2P 10DLC guide covers the registration side.

5. Seed-test to your own phones, then pilot

Send the final message to your team's phones: iPhone and Android, on different carriers. On an iPhone with Screen Unknown Senders on, texts from numbers not in contacts go to a separate list with no notification, and links stay unopenable until the person marks the sender as known.[19] Your seed test shows you what a first-time recipient actually sees.

Then send a pilot batch of a few hundred and watch the logs before you release the rest. HighLevel describes a "good" error rate as 0–6% and a "good" opt-out rate as 0–1%.[2] If the pilot drifts outside either, stop and find out why.

6. Set drip throttling under your daily cap

Never blast. HighLevel's drip mode sends bulk actions in batches of 1 to 10,000, repeated every set number of minutes, hours or days, inside the hours you choose.[20] Size the batches against your cap. Twilio puts T-Mobile's cap at up to 2,000 segments a day for a Low-Volume Standard brand.[21] HighLevel lists that tier at up to 6,000 a day.[22]

On T-Mobile, the daily cap is shared by every campaign under the same brand and tax ID, even across providers. A brand vetted at 50–74 gets 40,000 a day.[23] A 40,000-segment send at that tier uses the whole day's allowance, including what your reminder workflows needed.

Get this wrong and the damage spreads. When a HighLevel account crosses its limits, outbound SMS fails until 00:00 UTC.[2] That means every workflow, not just the blast.

7. Respect the send window, in the recipient's time zone

The federal rule bars telephone solicitations before 8 a.m. or after 9 p.m. in the recipient's local time.[12] Some states are stricter:

Rule	Earliest	Latest	Source
Federal, 47 CFR 64.1200(c)(1)	8 a.m.	9 p.m.	[12]
Florida, Fla. Stat. 501.616(6)	8 a.m.	8 p.m.	[4]
Oklahoma, 15 O.S. 775C (2022)	8 a.m.	8 p.m.	[5]
Maryland, Com. Law 14-4502(c)	8 a.m.	8 p.m.	[6]
Washington, RCW 80.36.390(8)	8 a.m.	8 p.m.	[24]

Examples, not a complete list. Washington's statute refers to calls; texts there are also governed by a separate commercial electronic messages law.

Time zones are where this goes wrong. A national retailer is now facing a class action alleging marketing texts sent outside those hours, including at 5:15 a.m. local time; those are allegations, not findings.[25] Check which time zone your drip's hours run in. If it's the account's, a 9 a.m. Eastern start reaches California at 6 a.m. For a national list, the simple safe window is 8 a.m. to 8 p.m. in the recipient's time zone.

8. Keep raw links out of the first text

A first text from an unfamiliar number that carries a link is the message most likely to be filtered. CTIA says senders who shorten links should use a shortener dedicated to their exclusive use.[14] We use trigger links on the brand's own domain and send the link in a follow-up, not in message one. Our carrier-filtering post-mortem shows what happens when you don't.

9. Count the segments and price the international numbers

Render the final copy and count segments. A plain GSM-7 text fits 160 characters, or 153 per segment when it runs longer. One emoji, curly quote or other non-GSM character switches it to UCS-2: 70 characters, or 67 per segment.[3] A 100-character reminder with one curly apostrophe becomes two segments, and 40,000 texts become 80,000 billable segments.

Then sort the list by country code. Twilio charges $0.0083 a segment in the US.[26] A text to Egypt costs $0.3959.[27] That's about 48 times more, and nobody notices until the invoice. Other countries also have their own marketing-text laws, so check before you include them.

10. Line up backup email

Have the same message ready to go by email before the text goes out. If carriers restrict the account mid-send, you switch channels instead of losing the reminder. We've done exactly that on a ticket send that hit a carrier restriction: slowed the drip and sent the message by email so registrants still got it.

The math for a 40,000-number send

This is a worked illustration at list prices, not a client result. Your provider's rates will differ; HighLevel's LC Phone rate card isn't Twilio's.

Line	Math	Cost
Line-type lookup, Twilio[1]	40,000 × $0.008	$320
Carrier lookup, Telnyx LRN (different product)[10]	40,000 × $0.0015	$60
Reassigned-number checks, RND at the Tier 2 rate[13]	40,000 × $0.006	about $240
Send, one segment, Twilio base[26]	40,000 × $0.0083	$332
Carrier fees, one segment	40,000 × $0.0035 to $0.005	$140 to $200
Same send at two segments	double both lines	$944 to $1,064
Fees on failed messages	$0.001 per failure	$10 per 10,000

List prices checked 2026-10-04. Carrier fees range from AT&T's $0.0035 to Verizon's $0.005 per segment.

Three things stand out. Validation costs about what one send costs. The segment count matters more than any lookup. And failed messages cost almost nothing in fees; what they cost is the account, when the failure rate trips its limits.

Validation also shrinks the send. If the list behaves like the old lists we see, 40–45% of records survive, so you pay to text roughly 16,000 to 18,000 numbers instead of 40,000.

That matters because usage is most of the bill. In our experience, on the event funnels we run, usage (email, SMS, carrier and A2P fees) runs 1.5–3x the HighLevel plan fee in launch months. That's our estimate; there's no industry benchmark for it.

Drip time. AT&T limits each campaign's speed by class: 240 messages a minute for classes E and F, up to 4,500 for A and B.[28] At 240 a minute, 40,000 segments take about 2 hours 47 minutes. Start well inside the send window.

International. At Twilio's list prices, 40,000 one-segment texts would cost $332 to Canada,[29] $2,240 to the UK[30] and $7,276 to Mexico.[31]

Opt-outs to expect. Postscript's 2026 benchmarks put ecommerce campaign unsubscribe rates between 0.33% (25th percentile) and 0.88% (75th).[32] On 40,000 delivered, that's 132 to 352 opt-outs. Klaviyo rates under 0.5% as great and 2% or more as critical.[33] Neither is an event list, so use them as rough bands for your pilot gate.

The SMS pre-flight checklist

• Validate line type; drop landlines and invalid numbers
• Dedupe; check reassigned numbers on aged lists
• Confirm the consent source for every segment
• Sending number attached to the registered A2P campaign
• Seed-test to your own phones, then pilot a small batch
• Drip under the daily cap, inside your carrier throughput
• Send window set in the recipient's time zone
• No raw link in the first text; trigger links on your domain
• Segments counted; international numbers priced
• Backup email ready

For how SMS fits with email authentication, A2P and consent, start with our deliverability and compliance guide. If you want a second pair of eyes before a big launch, book a strategy call.