Why does an SMS never land in spam, and what gets filtered instead?

SMS has no spam folder. That does not mean nothing is filtered — it simply happens earlier in the chain, and more quietly.

Where the filtering happens

At the operator. It looks at patterns: sudden volume spikes from an unknown sender, messages with suspicious links, or sender names that resemble a known brand. What is blocked simply does not arrive.

Why you barely notice

You get no "landed in spam" notification. You only see a status saying it was not delivered. That is precisely why the delivery report matters more here than with email.

What to avoid

Shortened links from free services everybody uses — those often appear in filter lists. Prefer a shortener on your own domain.

Sudden spikes from a new sender. Build the volume up.

Words and formatting that look like fraud: lots of capitals, urgent language, a link without context.

What you do instead

A recognisable sender, a link to your own domain, and a message the recipient is expecting.