What happens if…

Sending, templates and the Inbox: each case, what Gemmein does and what you do.

Sending

For notify(). A relay's email_person rides the same caps. The purchase email and Development's daily budget have their own sections: The purchase email and Development sends.

If…	What happens	What you do
Your domain is not verified for email yet	`409 sender_domain_required`. Nothing leaves, nothing is recorded and no cap is spent	Verify the domain on the Domains page. The same `key` then sends once
The person id is unknown, belongs to another environment, or the person is suspended	`404 not_a_customer`. Nothing is sent	Send to a person id from the same environment as your key
You retry with the same `key`	One email leaves. The retry answers `deduped: true` with the first send's `id` and spends no cap	Nothing
Two people get the same `key`	Both are sent. A key is scoped to its person	Nothing
Two sends with the same `key` arrive at once	The second answers `409 in_flight`. Once the first finishes, the same key answers `deduped: true`	Retry after a moment
A person has had 5 emails today and you send another	`429 notify_capped` with `resetAt`. Sends with `kind: "account"` are outside this cap	Wait for `resetAt`. Send sign-in, access and billing notices as `kind: "account"`
Your app has sent 200 emails this hour	The next answers `429 notify_capped` with `resetAt`, whatever its kind	Wait for `resetAt`
Your mail provider fails or refuses your address	`502 send_failed`. Nothing is sent from a Gemmein address instead, and the cap is handed back	Retry with the same `key`
Sends are switched off on the Emails page	Every `notify()` answers `403 sends_disabled`. Switching them back on restores sends, and Logs records each change	Switch sends on on the Emails page
The subject, the text or the person is missing	`400 no_subject`, `no_text` or `no_person`. A `kind` other than `event` or `account` is `400 invalid_kind`	Fix the call
A subject contains line breaks	They are removed before sending, so a subject cannot add mail headers	Nothing
Receiving is not verified yet	The email is sent with `replyRail: false`. A reply has no path back to your Inbox	Verify receiving on the Domains page, or tell people where to write
A person is erased	Their sends are removed from your records. Other people's sends are untouched	Nothing
The person's address bounced for good, or they marked your mail as spam	`200` with `sent: false`, `notSent: "address_bounced"` or `"address_complained"` and a `message`. Nothing leaves and no cap is spent. A relay's `email_person` and the purchase email skip it the same way. Each skip is counted and on Logs, and the person's page says why	Don't retry. To mail them again, turn their email back on from their page
10 of your customers' addresses have bounced or reported spam	Errors warns you, and again at 20, 30 and so on	Check how addresses are collected and what your emails say
Your domain is not verified and someone signs in	The sign-in code arrives from `<App name> (via Gemmein)`, with the footer Sent by Gemmein on behalf of <App name>. From a verified domain it arrives from `account`, with Powered by Gemmein	Verify a domain for email
Your provider refuses your domain for a sign-in code	The code is sent again from Gemmein's shared address with the shared footer, so the person can still sign in. Sign-in codes are the only email with this fallback	Check the domain on the Domains page

Templates

If…	What happens	What you do
A template uses a variable its email does not have	Sync refuses that file with `400 unknown_variable` and names the variables it has. The other files still sync	Use only the listed variables
A file's name is not one of the seven	It is refused with `unknown_template` and never synced	Rename it
There is a `sign-in.html`	It is never synced. The sign-in email takes no HTML	Write `sign-in.json`
`sign-in.json` has another key, a greeting or app name with a digit or an address, a colour that is not `#rrggbb` or is too light, or a logo that is not `https:`	`400 invalid_brand` with the reason	Fix the value
The logo cannot be fetched when you save: not a PNG, JPEG, GIF or WebP, over 200 KB, a redirect, or an error	`400 logo_unavailable` with the reason. Nothing is saved	Fix the address or the image, then save again
A template is over 100 KB	`400 template_too_large`	Host images at `https:` addresses and trim the HTML
A template holds a script, a form, an event handler, CSS maths or an `http:` image	It is saved with those removed, and sync lists what was removed	Nothing, or remove them from the file
`inbox-reply.html` has no `{{content}}`, or more than one	`400 content_slot`	Put it in once
An email has no template, or its template cannot be read or rendered	It is sent in Gemmein's plain design	Nothing
You save a template in Live	`409 templates_live_refused`	Save it in Development; go-live or promote copies it into Live
Your app has saved templates 60 times, or previewed them 120 times, this hour	`429 templates_capped` with `resetAt`	Preview locally with `npx gemmein emails preview`, which has no limit
You send a test	One email, subject [Test] …, to the address you are signed in with and no one else. It counts toward Development's 20 a day per app and 50 per account	Past that, wait for `resetAt`
You delete a file from `gemmein/emails/`	The cloud keeps the template. In `npx gemmein dev` it is removed at once	Run `npx gemmein emails remove <name>`

In the Inbox

If…	What happens	What you do
A person replies	The reply lands in the same conversation. A subject starting Re: or Fwd: joins the conversation it answers	Nothing
You open a conversation and do not reply	It is marked read and still needs a reply. Only your reply answers it	Reply
You close a conversation and they write again	It reopens, with the new message unread	Nothing
A person has waited 12 hours for your reply	Gemmein emails your owners and admins once for that wait. If you answer and they write again, a new wait starts	Reply. To stop these emails, switch the alert off on Settings → Notifications; the Inbox still shows the conversation waiting
A message's body cannot be fetched from the mail provider	The message shows without a body and says so	Choose Try again on the message
A person attaches a file	The message shows the file's name. The file itself is not kept	Ask them to send it another way if you need it
You start a conversation with someone who has not signed in	It is refused, and nothing is sent. The Inbox writes only to people who have signed in to your app	Ask them to sign in first
You start a conversation under a subject they are already waiting on	It is refused, and nothing is sent	Reply in that conversation
You have started 30 conversations in the last hour	The next new conversation is refused, and nothing is sent	Wait, then send it
Your domain is not verified for email	New conversation and Reply both say so, with a link to the Domains page, and send nothing. They never send from a Gemmein address	Verify the domain on the Domains page
Your provider refuses your address on a reply or a new conversation	Nothing is sent and nothing is recorded	Try again in a minute
A person is erased	Their conversation stays in your Inbox with their email address removed. Other people's conversations are untouched	Nothing
You reply to, or start a conversation with, an address that bounced or reported your mail as spam	It is refused with `409 address_suppressed`, and nothing is sent	Reach them another way
One sender emails your Inbox more than 20 times in an hour, or more than 300 emails in an hour arrive from people who are not your customers	The rest are dropped as spam, not stored, and counted. Errors says how many. Your customers and people you already have a conversation with still get through, each still at most 20 an hour	Nothing. It is usually a mail loop or spam

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Last updated 13 October 2026