The most common mistake we see businesses make with SMS is using it like email-but-faster. The second most common mistake is using email like SMS-but-longer. Both produce the same result: subscribers stop reading either one.
The two channels are not interchangeable. They earn the click on completely different terms.
The 90/10 rule
A working rule we use across every Mailelse client: at least 90% of marketing should be email, no more than 10% should be SMS. That ratio surprises businesses who have been told SMS has a 98% open rate and is therefore the future. It does, and it isn't.
SMS gets opened because it interrupts. The phone buzzes, the message takes a quarter-second to read, and the recipient is back to whatever they were doing. The interruption is the whole product. It is also the reason SMS is unforgiving — every send burns a small amount of patience, and the meter empties faster than most businesses think.
Email is invited. The subscriber chose to keep an inbox open all day. They open your message because the subject line earned the read at a moment they were already reading mail. Done well, email is a small habit. SMS is always, by design, an exception.
What email does that SMS can't
Email holds context. A paragraph of setup, an image, a comparison table, a link with a real description, a sign-off in the brand's voice. The reader can scroll, scan, save, forward, archive, and come back to it tomorrow. Email rewards the kind of message that takes thirty seconds to read and earns a thoughtful action — clicking through to compare two products, reading a story about how a customer uses the service, scheduling something a week out.
The newsletter, the launch announcement, the seasonal campaign, the customer-story essay, the multi-link roundup, the welcome series — all of it is email. None of it survives compression to 160 characters.
What SMS does that email can't
SMS earns the now. "The pickup window closes in 90 minutes." "Your appointment is confirmed for tomorrow at 3." "Restock alert: the size you wanted is back in for one more day." Anything where the value is time-bounded and the action is one tap.
Used this way, SMS feels like a service. Used as discount-blast or weekly-update, SMS feels like spam, and the unsubscribe rate proves it within four weeks.
The combined cadence
The clean structure we use for clients who run both channels: email handles the regular weekly relationship, SMS handles the occasional time-sensitive nudge. The two never duplicate each other. A subscriber who got the launch announcement in email does not also get it in SMS. The SMS list is a small subset — usually 20 to 30 percent of the email list — of customers who explicitly opted into time-sensitive alerts.
This is the structure that keeps both channels healthy over years instead of months.
What we set up
For every Mailelse client running both, we maintain the email list as the master and treat SMS as a tagged subset. SMS sends are scoped to genuine time-bounded events — never weekly cadence. The opt-in for SMS is explicit and separate, with its own consent record, because it has to be in most jurisdictions and because it should be in all of them.
You hand off both channels to the same team. We make sure the message lands on the right one, and that the subscriber on either list never feels like the other channel is treating them like fuel.