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What is carrier filtering and why are texts blocked?

Carrier filtering is the scanning mobile networks do on business texts to catch spam and scams before they reach phones. Texts that look risky can be blocked. Real alert texts sometimes get caught, because alarm wording can look like scam wording.

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Glossary

Carrier filtering

In plain English, with what it means for alert texts.

Illustration of Carrier filtering.

What carrier filters look for

Filters look at the words in a text, any links in it and the number it comes from. The rules are private and change often.

Words common in scams, like locked, blocked or claim, can trip a filter even inside a genuine alarm. The filter only sees the text, so it can't know a door or pump is behind it.

Why real alarms can look like spam

The same screen alarm, written two ways. The first says BLOCKED and may be held back. The second says CLOGGED, keeps the meaning and is less likely to be flagged.

  • Before: the word a filter may flag: Welco: [Intake 2] Screen BLOCKED, high diff pressure at 4:40 PM. Reply STOP to opt out.
  • After: the same alarm, reworded: Welco: [Intake 2] Screen CLOGGED, high diff pressure at 4:40 PM. Reply STOP to opt out.

A phone showing these alert texts: Before: the word a filter may flag, "Welco: [Intake 2] Screen BLOCKED, high diff pressure at 4:40 PM. Reply STOP to opt out."; After: the same alarm, reworded, "Welco: [Intake 2] Screen CLOGGED, high diff pressure at 4:40 PM. Reply STOP to opt out."

How to keep alert texts deliverable

A few habits lower the chance that a filter stops a real alarm.

  • Name the fault in plain words, and swap out words that scams often use.
  • Leave long web links out of the alert text. The alarm should make sense on its own.
  • Send from a number your company does not share, such as your own alert number.
  • Make sure every phone has opted in before it gets alerts.

Carrier filtering vs Welco's blocked words

A carrier filter works on the network, after a text leaves the sender. Welco's own check runs earlier. It holds any outgoing text with a blocked word, such as marketing or phishing wording, and shows why in your feed.

A held text is never sent and uses no credits. The stop words page lists what Welco holds. Other delivery terms are in the SMS alert glossary.

What filtering means for your alert texts

A blocked alarm usually shows up as not delivered on its delivery receipt, so check your reports after any quiet night. Welco uses alerts-only numbers that marketing senders never touch.

Often, changing one risky word is all it takes. For more trigger words and fixes, read why alert texts get blocked.

Frequently asked questions

Can a carrier block a text that is not spam?

Yes. Filters judge the words, links and sender, not the intent. A genuine alarm with scam-like wording can be stopped the same way a scam is.

Do carriers tell the sender when they filter a text?

Not always in plain words. The delivery receipt usually shows the text as not delivered, sometimes with a code. Welco reports turn that result into a short reason.

Where should I change a risky word in an alarm?

In the alarm system itself, in the message text, point name or tag description. Then every future alarm goes out with the safer word, to every phone. Changing one email only fixes that one alert.

Does a blocked alarm text use message credits?

If the network blocks it after Welco hands it over, yes, credits are used. If Welco holds it first because of a blocked word, no credits are used.

Keep real alarms clear of spam filters

Send from alerts-only numbers and reword the risky words once.

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7-day free trial, 15 message creditsCard required for verificationNo charge for 7 daysEmail reminder before billing