Transactional email API
A transactional email API that bills per message.
Most email APIs sell you a monthly tier sized for your busiest week and then charge you for it in your quietest month. Aslio has no monthly platform fee, no per-seat charge and no minimum commitment — you top up a prepaid wallet and spend it down at ₹0.02 a message — about $0.21 per 1,000 emails.
In short
A transactional email API sends one-to-one application email — receipts, password resets, invoices, alerts — over an HTTP request rather than an SMTP server you maintain. Aslio is a transactional email API priced purely per message at ₹0.02, roughly $0.21 per 1,000, with no monthly platform fee, no seat charge and no minimum commitment. Delivery events are included on every account.
- $0.21
- per 1,000 emails
- ₹0
- monthly platform fee
- 0
- seats to buy
- EU
- app hosted in Frankfurt
Code
One call sends the message
Bearer key, JSON body, done. The from address must be on a domain you have verified so the mail is signed with your own DKIM.
curl https://aslio.asli.one/v1/email/send \
-H "Authorization: Bearer as_live_…" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: invoice-4417" \
-d '{
"from": "Acme <billing@acme.com>",
"to": ["customer@example.com"],
"subject": "Your invoice is ready",
"html": "<p>Hello</p>",
"statusCallbackUrl": "https://acme.com/hooks/aslio"
}'What you get
What is included on every account
Including the free one. There is no delivery-data upsell here.
Idempotency that holds
Send with an Idempotency-Key and retry as often as you like. A duplicate replays the original response instead of sending twice — enforced by a unique index, not a check-then-write race.
Refunded when we fail
If a message is charged and then permanently fails, the wallet is credited back automatically and the key is released so your retry can succeed.
Suppression before billing
Hard bounces and complaints go on your do-not-mail list. Later sends to that address are rejected before you are charged, which protects your sender reputation and ours.
One-click unsubscribe
Marketing sends carry RFC 8058 headers, so Gmail and Yahoo show a native Unsubscribe button — required for bulk senders since 2024.
Delivery pushed to you
Sent, delivered, bounced and complained events arrive on your statusCallbackUrl webhook, on every account from the first message.
Your own sending domain
You verify your domain and sign with your own DKIM, so your reputation stays yours instead of being pooled with every other sender on a shared IP.
Why per-message pricing changes the maths
A tiered plan asks you to predict your volume. You pick the tier that covers your peak, then pay it in every month that is not your peak — and pay an overage the one month you guess low.
A prepaid wallet removes the prediction. Fifty thousand emails costs about $5 in total, whether you send them across a month or in one afternoon. A quiet month costs a quiet month's worth. There is nothing to downgrade and nothing to cancel.
This matters most to two kinds of sender: early products whose volume is small and lumpy, and established products with sharp seasonality. If you send a flat, large, predictable volume every month, a committed-tier vendor may still beat us and you should check.
Honestly
Where Aslio is not the right answer
- We hold no SOC 2 report and no ISO 27001 certification. If your procurement requires one, we will not pass it today and would rather say so now.
- SMS and WhatsApp are still in build. Email is the channel that ships today. Do not pick Aslio this week for a multi-channel launch next week.
- Support runs 09:30–18:30 IST (UTC+5:30). That overlaps European and Gulf afternoons and the edges of the North American day. There is no 24/7 desk.
- We are a young, small company — Asli One Global was incorporated in February 2026. That is a legitimate thing to weigh for a critical dependency.
FAQ
Frequently asked questions
What is a transactional email API?
It is an HTTP interface for sending one-to-one application email — receipts, password resets, invoices, shipping notifications — without running your own mail server. You POST the message and the provider handles delivery, authentication, bounce handling and reputation.
How much does Aslio charge?
₹0.02 per email, about $0.21 per 1,000, with no monthly platform fee, no per-seat charge and no minimum. You prepay a wallet and spend it down. An optional Pro plan at ₹999/month raises the rate limit to 100 requests a second and adds priority support and the Aslio Flow automation suite.
Is there a free tier?
There is no monthly fee at all, which is better than a free tier for most people — sending a hundred test emails costs about one rupee. You are never on a clock and there is nothing to expire.
Can I use my own domain?
Yes, and you should. You verify your domain and Aslio signs with your own DKIM, so your sending reputation is yours rather than pooled with everyone else on a shared IP.
Does Aslio support SMTP?
Yes, since 1 September 2026. aslio.asli.one:587, STARTTLS, your API key as the password. Messages sent over SMTP go through exactly the same pipeline as the REST API, so the price, sender rules, suppression list and delivery events are identical.
What about SMS and WhatsApp?
Both are in build, not shipping. Email is the channel that works today. When they land they will run on the same API key and the same prepaid wallet, which is the point of the product — but do not choose Aslio this week for a multi-channel launch next week.
Where is the data hosted?
The application runs on AWS in Frankfurt, Germany (eu-central-1), inside the EU. Outbound delivery goes through AWS Simple Email Service in Mumbai. Asli One holds no SOC 2 or ISO 27001 certification and does not claim one.
Top up ₹100. Send ten thousand emails.
Top up a wallet and send. No monthly platform fee, no seat charge, no minimum commitment — a hundred test emails costs about one rupee.
Asli One Global Private Limited · CIN U62011TN2026PTC190105