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Email Module for Nails

This is the email module for nails, it brings email capability to the app.

The email template

Every email is assembled from three views, concatenated and then run through Mustache in a single pass:

Body views are bare HTML fragments — a few paragraphs, a table, a button. They inherit the shell and its stylesheet, and should not open a <table> for layout or carry style attributes of their own.

The header and footer are two halves of one document. The header opens everything down to the content well and closes none of it — <html>, <body>, the .body-wrap table and its row, the .container cell, the Outlook ghost table, the .content div, the .main table and its row, and the .content-wrap cell — and the footer closes all nine in order. They are not independently overridable: replacing one means replacing both, and a copy taken today stops tracking upstream changes. Override a slot instead.

The shell

Customising it

Three layers, cheapest first.

1. Do nothing

The masthead calls Logo::discover(), which resolves a logo from the app's composer extra.nails.data.logo_url, then the APP_LOGO_URL config value, then a filesystem probe of assets/img/logo.{png,jpg,gif}. If it finds one you get a branded email header for free; if it does not, the app's name is set as text.

2. Set the content settings in admin

Under Admin → Settings → Email → Content:

Both are omitted entirely — no empty row, no stray whitespace — when blank.

Because Mustache runs after the three views have been concatenated, these values share the email's template context. The {{appName}} Team and Hope that helps, {{sentTo.first_name}} both work, as does the {{ config('FOO') }} syntax. They are emitted unescaped, which is the same trust boundary as the email template override admin — treat them as administrator-authored HTML.

3. Override a slot

Drop a file into application/modules/email/views/structure/slots/. It wins over the module's copy through View's normal resolution order; no registration, and no need to touch the shell or its tag-balance contract.

Each has a <slot>_plaintext counterpart for the text part of the email, which you should override alongside it. Slots receive $emailObject.

slots/styles.php is rendered inside <head> after the module's own <style> block, so anything it emits cascades over the framework. That is the hook for an app which compiles its own email CSS:

There is no CSS inliner in the pipeline, so this has to be an inline <style> block rather than a <link>.

The stylesheet

assets/sass/email.scss is a manifest; the framework itself is a set of partials under assets/sass/email/:

Every partial imports its own dependencies, so any one of them can be compiled on its own. Set your tokens before the import, or the !default wins:

Media-query and dark-mode rules live in the partial they belong to rather than a trailing responsive.scss, so cherry-picking components/button gets the button's narrow-viewport and dark rules with it.

Tokens are Sass variables rather than custom properties, which is a deliberate divergence from nails/common: Outlook renders with the Word engine, which has no var() support and no fallback which can recover a missing colour, so tokens have to compile down to literals. Everything is prefixed $email- because @import leaks globals.

assets/css/email.min.css is a committed build artefact. Run yarn build after changing anything under assets/sass/ and commit the result.

Class reference

Everything below is available to a body view.

Alerts — alert plus one of alert-success, alert-info, alert-warning, alert-danger. alert--success and friends work too.

Banners — alert alert-header is the subject banner and alert-header--warning / --danger / --success / --info are solid-fill bands. These belong to the shell; a body view rarely wants them.

Buttons — btn (or button) plus one of btn-primary, btn-secondary, btn-default, btn-success, btn-warning, btn-danger, btn-info, btn-link. Add btn-block for full width. btn--primary-style modifiers and the button-* aliases work as well.

A button fakes its padding with a border, because Outlook ignores padding on an anchor. The consequence, if you are writing a variant of your own: the padding ring is painted with the border colour, so border-color has to equal the fill. An outline variant draws its rule with a non-inset box-shadow.

For a single, important call to action, btn-table is the Outlook-hardened version — a one-cell table, so the whole area is clickable everywhere:

Tables — table, with table--list for a two-column label/value list, table--numeric to centre every column after the first, and table--plain for no borders or tints. Do not put role="presentation" on a data table.

Panel — panel with panel__header, panel__body and panel__footer. Works as a <div> or a single-column <table>. panel--plain sits on the card rather than being tinted by it; panel--brand adds a brand rule.

Other components — badge (badge--neutral, --success, --warning, --danger, --info), divider (--tight, --loose, --strong, --blank), hero with hero__caption, code / <pre> for monospaced output, and heads-up for a value the recipient has to read off the screen and use.

Utilities — alignleft / aligncenter / alignright and their text-left / -center / -right equivalents; text-muted, text-brand, text-small, text-tiny, text-large, text-bold, text-normal, text-uppercase, text-nowrap, text-break; valign-top / -middle / -bottom; mobile-only and desktop-only; last to drop a trailing margin; and spacing steps on a 4px scale — m-0 … m-7, mt-, mr-, mb-, ml-, mx-, my- and the p- equivalents (0, 4px, 8px, 12px, 16px, 24px, 32px, 48px).

Preheader — the snippet a client shows next to the subject in the message list. Set preheader in the email's data to fill it.

Client caveats

• No CSS inliner. Styling comes from the embedded <style> block only. Clients which strip it — notably the Gmail app signed in to a non-Gmail account — render close to unstyled. The HTML presentational attributes (width, align, valign, bgcolor) are kept as a partial fallback: the card keeps its 600px width, its white fill and its coloured banner, but not its padding, radii or type scale. Mobile clients which strip <style> generally scale the message to fit rather than scrolling it.
• Dark mode is prefers-color-scheme, paired with <meta name="color-scheme"> and <meta name="supported-color-schemes">. Honoured by Apple Mail, Mail on iOS and Outlook.com. Gmail ignores it and force-inverts on its own terms — do not spend an afternoon working out why the dark rules appear not to apply there. Nothing in the framework depends on dark mode being honoured; the light palette is the one that has to work. The email debugger's Light/Dark switcher is how you exercise these rules — but a good-looking dark pane is not evidence that Gmail dark is fine. See Previewing and testing.
• Outlook gets a <!--[if mso]> block which swaps the font stack for Arial and removes every radius, plus a ghost table which holds the card at 600px. The footer closes the ghost table the header opens.
• A logo discovered by Logo::discover() is used in both colour schemes. If yours only works on a light background, override slots/masthead.php.

Previewing and testing

In a development environment the view online link in the footer renders the email debugger, which shows the Mustache context, the HTML part in an <iframe> and the plain text part side by side.

The HTML pane has a System / Light / Dark switcher. System is the default and renders the email untouched, so it follows your desktop appearance and is the only pane that exercises the real prefers-color-scheme query. Light and Dark render copies with that query rewritten to always or never match, which is what lets you see both palettes without changing your OS appearance or reaching for DevTools. The pane is 680px wide so the 600px card previews its desktop layout; narrow the window to fall below the 640px breakpoint and see the mobile one.

The dark panes show what Apple Mail, Mail on iOS and Outlook.com do. They say nothing about Gmail — see the dark mode note under Client caveats.

To send real mail:

Admin → Utilities → Send test email does the same through the UI.