Email vs SMS for Black Friday is a channel decision: email delivers longer, richer, lower-cost messages to a large opted-in list, while SMS delivers short, immediate, higher-cost messages to a smaller list that has given separate consent.
The question is rarely which one to drop. Customers have not chosen one channel; they check both, and each performs a different job in the same week.
The practical questions are how much of the budget and audience each channel should take, how to avoid duplicate or intrusive messages, and how to stay on the right side of consent rules.
What you will learn:
- How email and SMS compare on cost, reach, speed and content
- The consent rules you must meet before you send a text
- Which job each channel should do in a Black Friday campaign
- Two worked cost-per-order examples with correct arithmetic
- A coordination plan and the mistakes to avoid
The Short Version
- Email is the workhorse: low cost per message, room for detail, suited to sequences.
- SMS is the nudge: short, immediate, costlier per message, and only for people who gave separate consent.
- Compare channels by cost per order, not cost per message.
- Coordinate with shared suppression: do not text people who just bought or clicked.
- Keep email spam complaints below 0.10% and never reach 0.30%; keep SMS opt-outs under watch.
Direct answer: use email as the main Black Friday channel for the full sequence, and add a small number of SMS messages, such as early access, launch and last chance, to consented subscribers, with each channel given a distinct role.
Email vs SMS: How They Compare
Side-by-Side Comparison
| Factor |
Email |
SMS |
| Cost per message |
Low |
Higher |
| Content |
Rich: images, layout, product grids |
Short text, a link, sometimes media |
| Consent needed |
Opt-in or lawful basis, depending on region |
Separate, explicit consent in most regions |
| Speed of reading |
Minutes to days |
Often minutes |
| List size |
Usually larger |
Usually smaller |
| Tolerated frequency |
Moderate to high with segmentation |
Low |
| Automation |
Mature: cart, browse, post-purchase |
Growing, often cart and shipping |
| Deliverability risk |
Spam folder, reputation |
Carrier filtering, registration |
| Best at |
Storytelling, catalogues, sequences |
Urgency, reminders, alerts |
These are general tendencies. Individual results vary by brand, list quality and offer.
What Each Channel Is Actually Good At
Email has space. It can show a product range, explain a bundle, carry a gift guide and build anticipation across several sends. It is also cheap enough to test, so you can learn from it.
SMS has attention. A text is short, read in context and hard to miss, which makes it suited to a sale that goes live now or ends tonight. The same intrusiveness means a poor text costs you more than a poor email.
Reach and Inbox Placement
Email faces filtering by mailbox providers, tabs and summaries, so reach depends on reputation and engagement. See Gmail promotions tab relevance and Apple Mail categories.
SMS faces carrier filtering and registration requirements. In the US, business texting over standard numbers generally needs registration under the A2P 10DLC framework, and unregistered traffic can be blocked or throttled. Check current carrier rules with your SMS provider.
Consent and Compliance
Why Consent Is the Dividing Line
Consent is the biggest practical difference. Your email list does not give you the right to text.
| Region |
Framework |
Key points for SMS marketing |
| United States |
Telephone Consumer Protection Act (TCPA) |
Prior express written consent for marketing texts using automated systems; identify the sender; honour opt-outs |
| United States |
CTIA messaging principles and carrier rules |
Clear opt-in, opt-out handling and message content standards |
| United Kingdom |
PECR and UK GDPR |
Consent required for electronic marketing, with a narrow soft opt-in for existing customers |
| European Union |
ePrivacy rules and GDPR |
Consent generally required; national rules vary |
This is an overview, not legal advice. Penalties for unwanted texts, particularly in the US, can be severe, so confirm your approach with a qualified adviser.
What Good SMS Consent Looks Like
- Separate: a dedicated checkbox or keyword, not bundled with email signup.
- Specific: says that marketing texts will be sent, roughly how often, and that message and data rates may apply.
- Recorded: you store when, where and how the person agreed.
- Reversible: STOP works instantly and is honoured.
- Time-aware: you respect quiet hours, commonly treated as 8am to 9pm in the recipient's local time.
For the email side of consent, see the email GDPR compliance checker and email marketing laws.
Growing an SMS List the Right Way
Offer a clear reason to join: early access, a sale alert or delivery updates. Use a preference centre, so subscribers can choose channels; see zero-party data and preference centers. Never import a purchased list or text a number gathered for another purpose.
Cost: Comparing by Cost Per Order
Why Cost Per Message Misleads
A text may cost many times more than an email, yet convert much better on a small, highly engaged audience. Comparing price per message alone ignores conversion. Cost per order, and ultimately profit per send, is the fair measure.
Cost per order = total channel cost / number of orders
Worked Example 1: Email and SMS Cost Per Order
All figures are illustrative; use your own platform pricing and results.
Email: 100,000 delivered emails with a platform cost of 0.002 per email.
- Cost: 100,000 x 0.002 = 200
- Click rate 2.5%: 2,500 clicks
- Click-to-order 4%: 100 orders
- Cost per order: 200 / 100 = 2.00
SMS: 20,000 consented subscribers, at 0.04 per text.
- Cost: 20,000 x 0.04 = 800
- Click rate 8%: 1,600 clicks
- Click-to-order 6%: 96 orders
- Cost per order: 800 / 96 = 8.33
SMS produces almost as many orders (96 versus 100) from a fifth of the audience, which is a strong result. But its cost per order is 8.33 against 2.00, about 4.2 times higher (8.33 / 2.00 = 4.17).
Whether that is acceptable depends on order value and margin. At an average order value of 50 and a 40% margin, each order contributes 20. Email nets 20 - 2.00 = 18 per order, SMS nets 20 - 8.33 = 11.67. Both are profitable, but email's contribution per order is higher.
The conclusion is not that SMS is bad. It is that SMS should be spent where its speed and conversion justify the extra cost, which is on time-critical messages to people most likely to buy.
Worked Example 2: What a Coordinated Plan Earns
A retailer has 100,000 email subscribers, of whom 20,000 also opted in to SMS.
Email-only plan: six emails to the whole list. Assume a blended 100 orders per send at 50 average order value.
- Orders: 6 x 100 = 600
- Revenue: 600 x 50 = 30,000
Coordinated plan: the same six emails, plus three texts to the 20,000 SMS subscribers (early access, launch, last chance). Assume each text sends 40 orders, but a quarter of those would have bought through email anyway.
- Text orders: 3 x 40 = 120
- Overlap (25% would have bought anyway): 120 x 0.25 = 30
- Incremental orders: 120 - 30 = 90
- Incremental revenue: 90 x 50 = 4,500
- SMS cost: 3 x 20,000 x 0.04 = 2,400
- Incremental contribution at 40% margin: (4,500 x 0.40) - 2,400 = 1,800 - 2,400 = -600
On these assumptions, the extra SMS loses 600. Change the assumptions and the answer changes: at 60 orders per text, incremental orders are 180 x 0.75 = 135, revenue is 6,750, contribution is 2,700 - 2,400 = 300.
The lesson is that incremental orders, not total orders, decide whether SMS pays. Measure it with a holdout group, and model the comparison in the email campaign ROI comparison calculator. All figures here are illustrative.
Assigning Roles to Each Channel
| Moment |
Email's role |
SMS's role |
| Pre-sale |
Teaser and preview |
None, or a join-the-list prompt |
| Early access |
Explain and show products |
Alert: your access is live |
| Launch |
Full offer and catalogue |
One-line alert with link |
| Mid-sale |
Reminder with new information |
Usually none |
| Cart abandonment |
Primary reminder |
Optional second nudge for high-value carts |
| Last chance |
Deadline and benefits |
Short deadline text |
| Post-purchase |
Confirmation, delivery, cross-sell |
Shipping and delivery updates |
Keep the principle: email explains, SMS prompts.
Coordination Rules That Prevent Annoyance
- Shared suppression. If someone bought, remove them from reminder texts and emails.
- Sequence, do not duplicate. Send the SMS only to people who have not clicked the same-day email, after a delay.
- Frequency cap per person. Across both channels combined, not per channel.
- Quiet hours. Text within local daytime hours.
- Unified identity. Link phone and email to the same profile so rules can work.
- One-click exits for both. Email needs working unsubscribe; see RFC 8058. SMS needs STOP.
Plan the combined volume against your holiday email sending schedule and the full Black Friday email sequence.
Message Design for Each Channel
SMS Copy Basics
- Identify the brand in the first words.
- State the offer, the deadline and one link.
- Keep it short; avoid ALL CAPS and multiple exclamation marks.
- Include opt-out wording where required.
- Use a branded short link rather than a generic one where your provider supports it, as some carriers filter common shorteners.
Example: "Brand: Early access is live. 25% off until midnight. Shop: link. Reply STOP to opt out."
Email Copy Basics
Email can carry the narrative. Use a clear subject line, a light layout and a single call to action. Keep message size down; see Gmail clipping. Check subjects with the subject line analyzer.
Measuring Success Across Both Channels
| Metric |
Email |
SMS |
| Delivery |
Delivered rate, bounces |
Delivered rate, carrier errors |
| Engagement |
Clicks (not opens) |
Link clicks |
| Conversion |
Orders per click |
Orders per click |
| Negative signals |
Complaints under 0.10%; unsubscribes |
Opt-outs (STOP), carrier complaints |
| Financial |
Revenue per message, cost per order |
Revenue per message, cost per order |
| Incrementality |
Holdout test |
Holdout test |
Do not use email open rate as a performance metric; Apple Mail Privacy Protection inflates it. See Apple MPP and open rates. Attribution across channels is tricky: see the email attribution calculator.
Common Mistakes
Texting the Email List Without Consent
Email permission does not carry over. This is the highest-risk mistake.
Comparing Cost Per Message Only
Judge by cost per order and incremental contribution.
Duplicating Every Email by Text
It doubles the noise and the cost. Give SMS a distinct job.
Ignoring Opt-Out Rates
A spike in STOP replies is a signal to cut frequency.
Sending Texts Outside Local Daytime
Quiet-hours violations carry legal and reputation risks.
Treating SMS as a Replacement
SMS lists are smaller and cannot carry the whole campaign. Email still builds the base.
Email builds the case and SMS closes it: let each channel do what it is best at, and measure the combination by incremental profit.
Key Takeaways
- Email carries the campaign; SMS adds urgency to a small consented audience.
- SMS needs separate, recorded consent; email permission does not transfer.
- Compare channels by cost per order and incremental contribution, not cost per message.
- Use shared suppression and sequence texts after email non-clicks.
- Keep complaints under 0.10% (never 0.30%) for email and watch opt-outs for SMS.
- Confirm local law with a qualified adviser before launching a text programme.
Sources and Further Reading
Related Articles
Related tools: Compare channels with the email campaign ROI comparison calculator, check cost with the email campaign cost estimator, and test attribution with the email attribution calculator.
This article provides general guidance and is not legal advice. Consent and messaging rules differ by country and change over time, and figures in worked examples are illustrative. Confirm requirements with a qualified adviser and your SMS provider.
