coss.com

Email for every user of your platform.

coss.com Email for platforms gives each of your users a sub-account with its own domains, sending reputation, quotas and suppression list, all on your API key.

Read the docs

How it works

Create a sub-account per user, give it a domain, and name it on each send. coss.com keeps its reputation, quotas and suppressions apart from everyone else's.

// 1. One sub-account per user, addressed by your own id.
await ...({
  : "Acme Bakery",
  : "user_8812",
  : { : 5000 },
});

// 2. The user's own domain: only this sub-account can send from it.
const { :  } = await ..({
  : "acmebakery.com",
  : "user_8812",
});

// 3. Send for the user.
await ..({
  : "user_8812",
  : "Acme Bakery <orders@acmebakery.com>",
  : "customer@example.com",
  : "Your order is ready",
  : "<p>Come and pick it up.</p>",
});

The email's subaccount_id, and the one in its webhook events and log lines, tell you which user it was for. The API reference lists every field.

Built for multi-tenant sending

One user's bounces, complaints or bad content never stop another's email.

A sub-account per user

Create one per customer of your platform and address it by its sub_… id or your own uid. Sub-accounts belong to an environment: sandbox keys see sandbox ones, live keys live ones.

Their own domains and tenant

A sub-account's domains send through its own Amazon SES tenant, so its sending reputation at the mail provider is its own. They don't count toward your plan's domain limit.

Shared domains

Users without a domain of their own send from one of yours that you mark shared_with_subaccounts, through your organization's reputation and your dedicated IPs if you have them.

Quotas

Set recipients per day, per second, or both on each sub-account. A send over one is refused with 429 quota_exceeded, and your other sub-accounts go on sending.

Reputation per sub-account

Bounce and complaint rates are measured per live sub-account. Past your thresholds, or when screening blocks one of its emails, only that sub-account is paused, with subaccount.paused and subaccount.reputation_warning webhooks.

Suppressions and stats

Its bounces, complaints and unsubscribes go on its own suppression list only. coss.email.subaccounts.stats() returns its recipients per day: sent, delivered, bounced, complained, failed and suppressed.

Every new sub-account's first emails are screened for spam and phishing, so a bad actor who signs up to your platform is caught early. Over SMTP, name the sub-account with the X-Coss-Subaccount header; in a batch, each email can name its own.

Specifications

The limits of a sub-account. The docs list each one in context.

Plans with live sub-accounts
Scale and Enterprise
Live sub-accounts on Scale
1,000
Live sub-accounts on Enterprise
Unlimited
Sandbox sub-accounts
100 per environment, free
Domains per sub-account
10
Domains awaiting verification
5 at once
Stats history
45 days
Streams
transactional email
Addressed by
id or your uid

Plans

Live sub-accounts are part of the larger plans. Sandbox ones are free everywhere.

Email for platforms is included on Scale and Enterprise, with up to 1,000 live sub-accounts on Scale. Email your sub-accounts send is billed to your organization per recipient, like any email.

See pricing for the plans.

Questions

What is a sub-account?
One of your platform's users, inside your coss.com environment. It has its own sending domains, its own reputation at the mail provider and at coss.com, quotas you set, its own suppression list and stats, and you send for it with the same API key by naming it on each send.
How do I send email on behalf of my customers?
Create a sub-account per customer with coss.email.subaccounts.create(), giving it your own id for that customer as uid. Then pass subaccount on each send, or the X-Coss-Subaccount header over SMTP, and the email counts toward that customer's quotas, reputation and suppressions.
Can my users send from their own domains?
Yes. Add a domain with subaccount set and the user publishes its DNS records like any domain. Only that sub-account can send from it, through its own Amazon SES tenant, so a pause there stops only that user. Users without a domain can send from one of yours that you share with sub-accounts.
What happens when one of my users sends spam?
coss.com measures each live sub-account's bounce and complaint rates on its own. Past the warning threshold its reputation becomes warning; past the suspension threshold, or when content screening blocks one of its emails, it is paused and only its sends are refused. Your other users keep sending, and you reinstate it once you've dealt with the cause.
Which plans include sub-accounts?
Live sub-accounts need a plan with Email for platforms, and each plan sets how many you can have. Sandbox sub-accounts are free on every plan, so you can build the integration first. The pricing page lists the plans.
Is my organization still responsible for its sub-accounts?
Yes. Sub-accounts are billed to you, your own reputation still counts everything they send, and if your organization is suspended all of them stop.

Works with

On the same key, SDK, webhooks and logs: nothing more to set up.

Compared

How it stacks up against the services you may be using, with sources.

Start with Email for platforms today.

Development keys record every request and event and deliver nothing, so you can build and test before you verify a domain. Hand your coding agent this prompt:

Add coss.com to this project: read https://coss.com/llms.txt, get a development key with `npx coss-cli init --agents`, and build and test with it.

Pricing