Channels: email, SMS/MMS, WhatsApp, push, web and ads
The Channels domain tests channel selection and the hard constraints that differ by channel. The exam expects you to know which channel fits a message, what consent and technical prerequisites each needs, and where a send will silently fail.
Split tests compare subject line, from name or content; send time optimisation picks a per-contact time from historical engagement. Link tracking, suppression and consent apply to every campaign send.
SMS and MMS
- Credit-based. A segment holds 160 GSM-7 characters; Unicode characters such as emoji or non-Latin script drop that to 70 per segment, and concatenation bills each part.
- Opt-in and opt-out keywords are mandatory, some jurisdictions restrict sending hours, and alphanumeric sender IDs are not supported everywhere.
- MMS carries media and is not available in every country, so it needs a fallback.
Requires the WhatsApp Business API, explicit opt-in and pre-approved templates for messages sent outside the 24-hour customer service window. Templates carry a category - marketing, utility or authentication - which affects approval and pricing. A rejected template blocks the send entirely.
Mobile app push
Requires an app with the SDK integrated, a device token per install, platform credentials and an explicit opt-in. Tokens rotate and uninstalls invalidate them, so audience size is always smaller than installs.
Web personalization and ads
On-site personalization and recommendations depend on the tracking script firing on the page and on enough behavioural history. Retargeting syncs segments to ad platforms as custom audiences using hashed identifiers; platforms enforce a minimum audience size, so small segments never serve.
Worked example
An order-dispatched notification targets one customer. Best option: a WhatsApp utility template if the customer has messaged within the last 24 hours. Otherwise SMS, because delivery matters more than richness. Push only if the app is installed and opted in. The reasoning is urgency plus certainty: utility templates are not marketing, the session window removes template friction, and SMS does not depend on an app install.
Traps that cost marks
- Counting an SMS as one credit when emoji force Unicode encoding.
- Sending WhatsApp marketing with no approved template or no opt-in.
- Retargeting a tiny segment that the ad platform silently ignores.
- Assuming push reaches everyone who downloaded the app.