Blog: Behind the scenes
How business texts work behind the scenes
9 posts on behind the scenes
Behind the scenes
RCS in the UK: what it means for business texts
iPhones have had RCS since iOS 18, on networks that switch it on. Which UK providers have, what RCS changes for business texts, and why SMS is still the floor.
17 October 2026 · 8 min read
Behind the scenes
Scheduling texts around the clock change
On 29 March 2026 the hour after 01:00 did not exist in London; on 25 October it happens twice. What the law and the tz database say, and how to schedule texts.
17 October 2026 · 9 min read
Behind the scenes
Sending a text exactly once: idempotency
A dropped connection leaves you not knowing whether a text went. The Idempotency-Key header, what the IETF draft and Stripe say, and how to build a safe retry.
17 October 2026 · 9 min read
Behind the scenes
SMS pumping: the fraud that targets your signup form
Twitter said it lost $60m a year to bot-driven verification texts. How SMS pumping works, what Enea and Twilio say it costs, and how a UK form stays out of it.
17 October 2026 · 8 min read
Behind the scenes
The 3G switch-off and your texts
Every UK 3G network is now off and 2G follows from 2029. Why SMS kept working through it, who is still on an old handset, and what a sender should check.
17 October 2026 · 8 min read
Behind the scenes
UK mobile numbers: what the numbering plan says
Not every 07 number is a mobile. Ofcom's Numbering Plan gives 070 to personal numbers and 076 to pagers, and its weekly data file shows who holds the rest.
17 October 2026 · 9 min read
Behind the scenes
Webhook signatures: why HMAC and how to check one
What RFC 2104's HMAC does, why a signed webhook beats a secret in the URL, how to compare in constant time, and the replay window a receiver should enforce.
17 October 2026 · 8 min read
Behind the scenes
What "delivered" means (and what it doesn't)
A delivery receipt is a network's word that a text reached a phone. What the 3GPP and SMPP standards say it proves, what it never can, and how to read a report.
17 October 2026 · 9 min read
Behind the scenes
Why a text can arrive late
Store and forward, validity periods and the 72-hour window: what 3GPP TS 23.040 and GOV.UK Notify say happens to a text that cannot be delivered right away.
17 October 2026 · 9 min read