SMS or Email? Let the Buyer Pick the Channel and the Hour
SMS gets opened, email gets ignored, and both claims are true for different shoppers. The channel is a preference, not a strategy, and the store that picks for the shopper will be muted by half its list.
SMS and email are not competitors. They are different channels for different messages to different shoppers, and the shopper is the one who should choose. SMS is opened fast and read almost always, which makes it right for time-sensitive messages: an order shipped, a delivery today, a flash sale ending in hours. Email is cheaper, richer, and easier to ignore, which makes it right for content that can wait: a new collection, a guide, a restock notice. The mistake is picking one channel for the whole list. A shopper who wants SMS for shipping updates and email for everything else is giving you a routing rule, and a store that sends the shipping update by email and the sale by SMS has it backwards. Ask the shopper, store the answer per message type, and respect it.
The hour matters as much as the channel
A text at 9 a.m. is a notification. A text at 9 p.m. is an interruption, and the shopper will remember which one it was. SMS carries an expectation of timeliness that email does not, and that expectation cuts both ways: a delivery update at 8 a.m. is welcome, a promotion at 10 p.m. is a reason to opt out. The preference to capture is not just the channel but the window: morning, afternoon, evening, or no preference, stored per shopper and applied per send.
Email has its own timing rule, and it is looser. A marketing email sent at 6 a.m. sits in the inbox until the shopper is ready, which is why email tolerates a wider window. The cost of a mistimed email is a delete. The cost of a mistimed text is an opt-out, and an opt-out is permanent in a way a delete is not. Treat SMS timing as a promise and email timing as a suggestion.
Related reading on this site: PrefEngine and Stale Preferences Are Worse Than No Preferences cover the neighbouring problems in more depth.
Price the channel honestly
SMS costs per message, usually a few cents, and the cost scales with volume and with length. A store sending 100,000 texts a month is paying real money, and the return has to justify it. Email costs fractions of a cent per send, which is why it tolerates the long tail of content that SMS cannot. The right question is not which channel is better. It is which messages earn the per-message cost of SMS, and the answer is usually the short list: shipping, delivery, order issues, and the occasional high-intent promotion.
The compliance cost matters too. SMS is regulated more tightly than email in most markets: explicit consent, a clear opt-out in every message, and quiet hours in some jurisdictions. A store that treats SMS like email, same list, same cadence, same content, will learn about the difference from a complaint, not from a dashboard. Collect SMS consent separately, store it separately, and never move an email subscriber to SMS without an explicit opt-in.
Store the preference per message type, not per shopper
A shopper is not an email person or a text person. They are an email person for the newsletter, a text person for the delivery, and neither for the survey. The preference center should capture channel per message type: transactional messages, marketing messages, and back-in-stock alerts, each with its own channel choice. A single channel preference per shopper forces a false choice and guarantees that half the messages go to the wrong place.
The implementation is a routing table, not a field. When a message is generated, the sending system looks up the shopper's preference for that message type and routes accordingly, with a fallback to email when no preference is stored. The fallback matters: a shopper who never set a preference should get email, because email is the channel that tolerates being the default. SMS as a default is how a store loses a list in a month.
Frequently asked questions
Is SMS better than email for marketing?
Neither is better in general. SMS is opened fast and read almost always, which suits time-sensitive messages like shipping updates and flash sales. Email is cheaper and richer, which suits content that can wait. The right channel depends on the message and the shopper.
What time should marketing texts be sent?
Inside the shopper's stated window, and never late at night. A text at 9 a.m. is a notification, a text at 10 p.m. is an interruption, and the cost of a mistimed text is an opt-out, which is permanent in a way deleting an email is not.
Can a store move email subscribers to SMS?
No, not without explicit opt-in. SMS consent must be collected separately and stored separately, and it is regulated more tightly than email in most markets, with a clear opt-out required in every message.
Should channel preference be stored per shopper or per message type?
Per message type. A shopper may want SMS for delivery updates and email for the newsletter. A single channel preference per shopper forces a false choice and sends half the messages to the wrong place.