5 message patterns that get SMS and WhatsApp messages flagged as spam

How filtering actually works

There is no single list of banned words that, once avoided, guarantees delivery.

• SMS carriers and gateways score messages on their content, the sender, the volume and how recipients react. In India, where business SMS templates must be registered under the DLT rules, gateways such as Way2SMS can also reject messages that contain particular words or do not match a registered template.
• WhatsApp looks mostly at behaviour: how many people block or report you, how fast you send, whether people reply, and whether you write to people who never wrote to you.

So the patterns below matter in two ways: they trip content filters directly, and they make people more likely to block or report you, which hurts every message after.

Spam trigger words

Words and phrases used by scams and aggressive marketing raise a message's spam score on their own:

• money and prize language: "free", "winner", "cash", "prize", "guaranteed", "risk-free", "loan", "credit";
• urgency: "act now", "limited time", "urgent", "last chance", "expires today";
• requests that look like phishing: "verify your account", "confirm your details", "click below", "your account is suspended".

You do not need to remove every one of these words. A genuine order message can say "free delivery". The problem is a message built around them. Say what happened and what the customer can do, in plain words.

Overly promotional

A message that is all offer and no information looks like advertising from a stranger, even when it comes from a shop the customer used.

• Lead with something specific to the person: their order, their appointment, the product they asked about.
• Keep promotions for people who agreed to receive them, and send them rarely.
• Never make a promotional message look like a transactional one, such as a fake "your order" opening that turns into an ad.

Caps & emojis

ALL CAPS, rows of exclamation marks and strings of emojis are classic spam signals, and they read as shouting.

• Use normal sentence case. Capitalise a single word if it needs emphasis.
• One emoji can make a message friendlier. Five make it look like a chain message.
• On SMS, one emoji switches the whole message to a different encoding, which cuts the length of each part from 160 characters to 70 and can turn one message into three. Paste a message into our SMS character counter to see which characters do this.

Links that hide where they go

Links are the most common feature of phishing, so filters treat them with suspicion.

• Avoid public URL shorteners. They hide the destination and are heavily used by spammers.
• Link to your own domain, the one customers know.
• Leave links out of verification codes entirely.
• On WhatsApp, avoid a link in the first message to someone who has not written to you before.

Opt-out

The fifth pattern is a message with no way to stop the next one. When people cannot stop your messages, they block or report you instead, and on WhatsApp those reports count against your number.

• In marketing SMS, include an opt-out instruction such as "Reply STOP to unsubscribe" where the rules of the country require it, and honour it straight away.
• On WhatsApp, tell people they can reply STOP, and remove them when they do.
• Transactional messages such as codes and order updates do not usually need an opt-out line, but stopping them on request is still good practice.

Poorly written

Spelling mistakes, strange formatting and an unclear sender are signs of scams that people have learned to recognise. Say who you are in the first words ("Oxtro Shop: your order..."), write complete sentences and read each template once more before it goes to a thousand people.

Additional practices

• Send only to people who asked to hear from you. Bought, scraped or guessed lists are the fastest way to get filtered on SMS and banned on WhatsApp.
• Make each message personal. Template variables such as the customer's name and order number make messages different from each other, which looks less like bulk spam and is more useful.
• Send at sensible times. Messages at night get blocked more often.
• Pace bulk sends. Spread campaigns over time instead of sending everything at once. Oxtro campaigns send through a queue at a rate you set.
• Warm up new numbers. A new number that suddenly sends hundreds of messages looks like spam. Our number safety guide explains how to warm one up.
• Watch your failure and block rates. A rise in either is the first warning. Slow down and look at what changed.

Broader trends

Filtering is getting stricter on both channels. More countries require businesses to register their SMS senders and templates before sending, such as 10DLC in the United States and DLT in India. Carriers increasingly filter on how recipients react, not only on content. WhatsApp keeps tightening limits on unsolicited messages to protect its users.

The direction is the same everywhere: messages people expect and want get through, and everything else has a harder time. The best protection is not a clever way around the filters, but a list of people who want your messages and content worth reading.

If you are choosing between channels, read SMS vs WhatsApp for business messages.