Blog/Channels
Channels · 11 Nov 2025 · 7 min

Choosing a channel per message: a framework that holds up

Email, SMS, WhatsApp and push each have a cost, a permission and a tolerance for interruption. Three questions decide which one a given message belongs on, and they take about a minute.

Four channels, four different costs and four different permissions

Multi-channel marketing usually degrades into sending the same message everywhere, which costs more, annoys people faster, and produces no more revenue than the best single channel would have. The alternative is not complicated: decide per message, using the properties the channels actually differ on.

The three questions

  1. Does it have a deadline measured in hours? If yes, an interruptive channel earns its place. If no, email.
  2. Is it personal to this individual? A named product they asked about, their order, their delivery. Personal messages justify a per-message cost; broadcasts rarely do.
  3. Do you hold consent for that channel specifically? If not, the answer is email, or nothing, and the real task is asking properly rather than reinterpreting a tick box you already have.

Two yeses and a consent means consider SMS or messaging. Anything else is email.

What actually differs

Cost per message is the property that should shape strategy and the one most often ignored until the invoice.
  • Email: effectively free per message, unlimited length, easy to ignore, and the only channel where a weekly newsletter makes sense.
  • SMS: real cost per message varying more than tenfold by country, 160 characters before it becomes two, read within minutes, and sender IDs regulated per market.
  • WhatsApp and Viber: priced per message or conversation with marketing dearest, templates approved in advance, and a reply window that makes conversation cheap.
  • Web push: free, instant, and the permission is lost permanently rather than gradually when you overuse it.
Cost per message is the fastest way to narrow the choice
Cost per message is the fastest way to narrow the choice

The common cases

  1. Weekly or monthly newsletter → email. Nothing else, ever.
  2. Order confirmation and shipping → email, plus a message channel if the customer chose one. Transactional, so no marketing consent needed, and it should come from a different subdomain than campaigns.
  3. Abandoned cart → email first. A second touch on SMS only for high-value carts, where the per-message cost is justified by the order size.
  4. Back in stock → whichever channel they requested it on. This is the clearest case for push or messaging, because it is personal and time-bound.
  5. Flash sale ending tonight → email to everybody, SMS to the top decile by past value. Not SMS to the whole list.
  6. Win-back after a year → email. If email has failed three times, one message on another consented channel to your highest-value lapsed customers.
  7. Post-purchase care → email, and messaging if you want replies, which are the most valuable conversations you will have.

One frequency cap across all of them

The failure mode of multi-channel is not choosing badly, it is choosing several times for the same message. Somebody receiving an email, an SMS and a push about one sale has been contacted three times about one thing and will remember it as harassment rather than as a campaign.

  • Cap per person per week, counted across every channel, not per channel.
  • Count transactional separately — a delivery update is not a marketing contact.
  • Give the cap to the highest-value message, not the first one that queues.
  • Make it visible on the campaign screen, so somebody scheduling a send can see who is already at the limit.

Before any of the above, the honest count: how many people have actually consented to each channel. Most shops discover that their SMS-consented audience is a tenth of their email list and their messaging audience is smaller still.

That number, not the channel's theoretical reach, is what a plan should be built on. It also tells you where to put the effort — usually into asking properly at checkout rather than into a second platform.

Sources and further reading (4)
  1. ePrivacy Directive 2002/58/EC — Article 13
  2. EDPB — Guidelines 05/2020 on consent
  3. WhatsApp Business — Pricing
  4. 3GPP TS 23.038 — SMS character sets

Checked on 23 September 2026. Provider prices, mailbox rules and legal guidance change — verify anything you plan to act on.

One brief, every channel, one cap

Drafts per channel from a single brief

Auralata writes a draft for each channel you have switched on from one brief, keeps consent separate per channel, and can cap how many marketing messages one person gets in a week across all of them.

Start now See how it works
One brief → four draftsconsent per channel
Email12,480
SMS · top decile only119
WhatsApp318
64 people would hit the weekly cap — held from SMS.
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