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They look like the same product. One sends a receipt to a person who just paid; the other sends one message to everyone on a list. The tooling, the consent rules and the deliverability trade-offs are all different, and the free tiers tell you which problem each was built for: 3,000 emails a month capped at 100 a day on one side, and 10,000 subscribers for nothing on the other.
Both figures checked 7 October 2026. Neither service pays me anything.
What is the actual difference?
| Transactional | Marketing | |
|---|---|---|
| Triggered by | something the recipient did | your calendar |
| Audience | one person | a list |
| Must arrive | in seconds | some time today |
| Consent | implied by the purchase | explicit, and revocable |
| Failure looks like | a customer without their file | a lower open rate |
The last row is the one that decides your setup. A marketing email that lands in Promotions is a disappointing Tuesday. A receipt that lands in Promotions is a support ticket, and possibly a chargeback.
Mixing them costs you the thing that makes transactional mail arrive: a sending reputation built on messages people asked for, from a domain that does not also send campaigns.
What do the free tiers actually give you?
| Resend, free | Kit, free | |
|---|---|---|
| Limit | 3,000 emails/month, 100/day | 10,000 subscribers |
| Domains | 3 | n/a |
| Retention | 30 days | n/a |
| Also includes | API, SMTP, webhooks | unlimited broadcasts, forms, landing pages, selling digital products |
| First paid tier | $20/month, 50,000 emails | $33/month |
Kit's free plan is unusually generous for the category — ten thousand subscribers with unlimited broadcasts is more than most people reading this will reach, and the paid tier buys automations rather than capacity.
Resend's free plan is sized for a small shop, with one sharp edge.
Which limit actually bites?
The daily one, not the monthly one.
Three thousand emails a month is 100 a day on average, and a small shop sends nowhere near that. But the cap is not an average — it is a hard 100 in a day. The day it matters is the only day you would mind: a video lands, two hundred people download the free book in an afternoon, and the second hundred wait.
That is the whole argument for the $20 tier, and it is worth making the decision on that scenario rather than on the monthly total. If your delivery is the product, a queue is not a minor degradation.
The Short Version
Every conclusion from all eight playbooks — 97 chapters, condensed. Free.
What makes the mail arrive at all?
Three DNS records, and they are not optional any more.
SPF says which servers may send for your domain. DKIM signs each message so the receiver can check it was not altered. DMARC tells receivers what to do when the first two fail, and publishes where to send reports. Both services above support all three, and both will walk you through it when you add a domain.
The part worth knowing: these are per-domain, and they are the reason sending receipts and campaigns from the same subdomain is a risk rather than a preference. Reputation attaches to the sending domain. Separate the two and a bad campaign cannot take your receipts down with it.
Do this once, when you add the domain, before you send anything to anyone. Retrofitting authentication after a month of mail going to spam means waiting out a reputation you already damaged.
Which should you set up first?
Transactional, without hesitating.
Until the thing you sell gets delivered automatically, you do not have a shop — you have a payment link and a promise to check your phone. How to sell a digital product without a platform covers that side of it.
A newsletter before you have anything to deliver is a list you will feel guilty about. Collect addresses from day one by all means, but the automated send that matters on day one is the one triggered by a purchase.
Do you need both?
Eventually, and sooner than you would guess.
The moment you have a free thing people sign up for, you have a list, and a list wants a tool that handles unsubscribes, segments and landing pages properly. Doing that by hand from a transactional API means reimplementing consent management, which is both tedious and the part regulators care about.
The practical split:
- Transactional service: receipts, download links, password resets, anything triggered by an action.
- Newsletter tool: the sequence after someone downloads the free thing, and anything you decide to send.
Use different sending subdomains for the two. If your campaigns ever get marked as spam at scale, you want that reputation damage contained to the subdomain that sends campaigns, not the one that sends receipts.
When is a newsletter tool the wrong purchase?
When you are buying automations before you have an audience.
The free tier covers ten thousand subscribers. Paying $33 a month to automate sequences for a list of forty is buying the machinery for a problem you do not have yet — and the sequence you would write today is one you will rewrite once you know what those forty people actually want.
Upgrade when the manual version has become genuinely annoying. That is a real signal. "It would be more professional" is not.
Where these numbers came from
Resend's and Kit's published pricing pages, both checked 7 October 2026, in US dollars. Plan contents change; the distinction between the two categories does not.
If the list is the thing you want to build, The Affiliate Playbook is the one that covers what to do with it once it exists.
Tools in this piece
| Tool | What it does | Price |
|---|---|---|
| Resend | Transactional email that actually arrives. | Free tier |
| Kit | Email platform for creators. The list is the only thing you actually own. | Free under 1,000 subs |
| Stripe | Payments and subscriptions. The standard, and integrating it is a matter of asking. | Free, percentage per sale |
| Vercel | Hosting. Puts a project live on a real address with one command. | Free tier |
Every tool has its own page with the price, who should skip it and what to check before paying. Some links are affiliate links.
Questions people ask
What is the difference between transactional email and marketing email?
Transactional email is one message to one person triggered by something they did — a receipt, a download link, a password reset. Marketing email is one message to a list on your schedule. They have different deliverability profiles, different consent rules and different tools.
Can you send your receipts from a newsletter tool?
Technically often yes, and it is a bad idea. Receipts have to arrive within seconds and must not be filtered as promotional. A newsletter platform is optimised for the opposite trade-off, and an unsubscribe from your list should never stop someone receiving the file they paid for.
What does Resend's free tier include?
Checked 7 October 2026: 3,000 emails a month, capped at 100 a day, 3 domains and 30-day data retention. The first paid tier is $20 a month for 50,000 emails with no daily limit.
What does Kit's free plan include?
Checked 7 October 2026: up to 10,000 subscribers, unlimited landing pages and forms, unlimited broadcasts, tagging and segmentation, and the ability to sell digital products. The Creator plan is $33 a month and adds automations and sequences.
Which should you set up first?
Transactional, every time. Until something you sell gets delivered automatically you do not have a shop. A newsletter with nothing to deliver is a list you will feel guilty about.
Does the 100-a-day limit matter?
Only in one scenario, and it is the bad one — a launch day where receipts queue behind the cap. Monthly totals are rarely the constraint; a single busy day is.