Comparison
Email carries detail and SMS carries urgency, and the two are governed by different consent rules that you cannot borrow from one another. Most stores should end up with both, but not at the same time and not for the same messages. The order to build them in, and the split of flows between them, follows from what you sell, how often people reorder and where your customers live.
By CartKernel · Last reviewed 2026-09-07
Option A
A permission channel with room for images, product blocks and explanation, suited to campaigns, education and the long tail of lifecycle messages a store needs.
Best for
Option B
A short, immediate channel read within minutes, suited to time-bound messages where the value of arriving now outweighs the value of saying more.
Best for
Side by side
| Criterion | SMS | |
|---|---|---|
| Consent | Permission to email, gathered at signup or checkout | Separate express consent to text, never inherited |
| Message length | As long as the message needs | A line or two, with a link |
| Reading window | Hours to days | Minutes, usually |
| Cost per send | Driven by list size and platform plan | Charged per message, so volume is a real constraint |
| Content | Images, product blocks, formatting | Plain text, sometimes an image, always a link |
| Timing rules | Send-time optimisation, few legal limits | Quiet hours by jurisdiction must be respected |
| Registration | Domain authentication and warm-up | Number registration and campaign vetting with carriers |
| Tolerance for frequency | Higher, with segmentation | Low, and unsubscribes are immediate |
An email address given at checkout does not authorise a text message. SMS requires its own express, provable consent for the specific programme, collected with clear disclosure at the point of opt-in, and the record of that consent has to be kept. In Canada the rules for commercial electronic messages are strict about how consent is obtained and evidenced, and in the United States texting programmes carry their own requirements around consent, identification and opt-out handling.
There is also an operational layer that email does not have. Sending numbers are registered and programmes are vetted before traffic flows, quiet hours apply by jurisdiction, and stop requests have to be honoured immediately and permanently.
None of this makes SMS difficult, but it does make it deliberate. Plan the opt-in wording, the confirmation message and the record keeping before the first send, and keep the two lists genuinely separate in the platform so a rushed campaign cannot cross them.
Email suits any message a shopper may want to reread. Welcome sequences that introduce the brand and the range, post-purchase education about care, sizing or setup, browse and category follow-ups, replenishment reminders with product blocks, review requests, and the campaign calendar that keeps the list warm between purchases.
SMS suits messages with a clock attached. A drop going live at ten, a restock on a size that sells out, the last hours of an offer the customer already showed interest in, a delivery exception, or a reorder nudge for a consumable that is due about now. Each is short, expected and immediately actionable.
Abandoned cart and checkout flows are the place both channels meet. A common pattern is an email first, since it can carry the cart contents, then a single text later in the window for people who opted into both. The point is to add a channel where it changes the outcome, not to duplicate the same message twice.
Keep them in one platform or one integrated stack so that suppression, segmentation and reporting are shared. The failure worth avoiding is a customer receiving a text about an offer twenty minutes after the email about the same offer, then a review request while a support ticket is open.
Set global rules the whole programme obeys. A maximum number of marketing messages per person per week across both channels. Suppression of anyone who ordered in the last few days from promotional sends. Transactional and shipping messages exempt from marketing frequency caps but still checked for tone.
Measure at the programme level. Revenue per recipient, repeat purchase rate and unsubscribe rate per channel say more than open rates, and SMS in particular should be judged against its per-message cost. Grow both lists in the same places, at signup, at checkout and after delivery, with separate checkboxes and honest expectations about what each channel will send.
The honest bottom line
Build email first. It carries every message type, it costs nothing extra to send to one more subscriber on most plans, and the flows built there become the backbone of retention. Add SMS once the email programme is running and there is a category of message where minutes matter, such as drops, restocks or reorder cycles. Stores selling consumables, limited releases or anything with a fast decision window get the most from the pair. Stores selling considered, infrequent purchases usually find email does almost all the work, with SMS reserved for shipping updates and the occasional genuine deadline.
We will tell you which fits, with your numbers.
No. Consent to email is not consent to text, and phone numbers collected for shipping or order updates are not a marketing list. Texting requires its own express opt-in for that programme, with the disclosure shown at the point of consent and a record kept of when and how it was given.
The ones where arriving now changes the result: back-in-stock alerts, launch and restock notifications, the final hours of an offer someone already engaged with, and delivery updates. These are welcomed rather than tolerated, which protects the list while you learn what the channel is worth.
Less often than it emails. There is no universal number, so start conservatively, watch the opt-out rate on every send, and treat a rising rate as the signal to slow down. Sending only when there is a genuine reason keeps a small list far more valuable than a large tired one.
They do not, and there are advantages to keeping them together. Shared profiles mean one suppression list, one view of frequency and one revenue report per customer. Separate tools can work, but someone then has to keep segments, quiet periods and unsubscribes aligned by hand.
A free Growth Analysis ranks what your store should fix first, by revenue at stake.