What channel are Email and SMS in GA4 — Google's official spec has the answer

Have you ever sent a newsletter campaign, checked GA4 the next morning, and found that none of the traffic landed under the Email channel? Or wondered why your SMS blast got bucketed into Referral instead of SMS? If you ask five marketers what channel Email, SMS, and Mobile Push land in inside GA4, you will get five different guesses. "Probably Referral, or (other)?" is the most common answer. But there is no guesswork involved. GA4 has an official Default Channel Group spec that decides exactly which of the 23 channels every visit gets classified into, based on the utm_source and utm_medium values. Google publishes the full logic, and operators cannot override it on the default report. In this post, I decode the official Email, SMS, and Mobile Push judgement rules straight from the public documentation, so you stop guessing and start naming UTMs correctly on the first try. TL;DR Email channel rule is satisfied when utm_medium=email (or three alternate spellings). The