diff --git a/docs/public-hosting.md b/docs/public-hosting.md
index 11ca407..8bb0408 100644
--- a/docs/public-hosting.md
+++ b/docs/public-hosting.md
@@ -28,7 +28,8 @@ on a LAN.
 
 To let someone else in, send them an invite: **Settings → People → Invites** makes a link that
 works once, expires (a week by default), and can be pinned to one email address. It
-lets that one person register while registration stays closed.
+lets that one person register while registration stays closed. With email set up (below) and an
+address filled in, **Create and email** sends the link to that address as well.
 
 **2. Terminate TLS in front of it, and forward the scheme.** The app marks the
 session cookie `Secure` and sends HSTS only when it can tell the request arrived over
diff --git a/frontend/src/components/InviteList.vue b/frontend/src/components/InviteList.vue
index 31eb7a8..27c628a 100644
--- a/frontend/src/components/InviteList.vue
+++ b/frontend/src/components/InviteList.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { onMounted, ref } from "vue";
+import { computed, onMounted, ref } from "vue";
 import { api } from "../api/client";
 import { errorMessage } from "../api/errors";
 import { appLink } from "../router/links";
@@ -7,6 +7,7 @@ import BaseButton from "./BaseButton.vue";
 import BaseInput from "./BaseInput.vue";
 import OneTimeSecret from "./OneTimeSecret.vue";
 import { toastOnFailure, useLoad } from "../composables/useAction";
+import { useConfigStore } from "../stores/config";
 
 // Admin: invite one person to register while registration stays closed (#5172).
 // The server keeps only a hash of each invite's token, so the link is shown once,
@@ -38,17 +39,30 @@ const days = ref(7);
 const creating = ref(false);
 // The link for the invite just made. Never retrievable again once dismissed.
 const freshLink = ref("");
+const freshNote = ref("");
+
+// Emailing the link (#5917) needs email set up and an address to send it to. The
+// server says whether email is on in the same flag the sign-in page reads.
+const config = useConfigStore();
+const sendEmail = ref(true);
+const canEmail = computed(() => config.passwordResetByEmail && email.value.trim() !== "");
 
 async function create() {
   creating.value = true;
   error.value = "";
   freshLink.value = "";
   try {
-    const res = await api.post<{ invite: Invite; token: string }>("/api/invites", {
-      email: email.value.trim() || null,
-      days: days.value,
-    });
+    const to = email.value.trim();
+    const res = await api.post<{ invite: Invite; token: string; emailed?: boolean; email_error?: string }>(
+      "/api/invites",
+      { email: to || null, days: days.value, send_email: canEmail.value && sendEmail.value },
+    );
     freshLink.value = appLink({ name: "register", query: { invite: res.token } });
+    freshNote.value = res.emailed
+      ? `Emailed to ${to}. The link is here too, in case it's easier to send yourself.`
+      : res.email_error
+        ? `${res.email_error} Send this link to ${to} yourself.`
+        : "Send this to the person you're inviting.";
     invites.value = [res.invite, ...invites.value];
     email.value = "";
   } catch (e) {
@@ -100,7 +114,7 @@ onMounted(() => {
     <OneTimeSecret
       v-if="freshLink"
       :value="freshLink"
-      note="Send this to the person you're inviting."
+      :note="freshNote"
       @done="freshLink = ''"
     />
 
@@ -123,7 +137,13 @@ onMounted(() => {
           <option v-for="l in LIFETIMES" :key="l.days" :value="l.days">{{ l.label }}</option>
         </select>
       </div>
-      <BaseButton type="submit" :loading="creating">Create invite</BaseButton>
+      <BaseButton type="submit" :loading="creating">{{
+        canEmail && sendEmail ? "Create and email" : "Create invite"
+      }}</BaseButton>
+      <label v-if="canEmail" class="flex w-full items-center gap-2 text-sm text-neutral-700 dark:text-neutral-300">
+        <input v-model="sendEmail" type="checkbox" class="h-4 w-4 accent-brand" />
+        Email the link to {{ email.trim() }}
+      </label>
     </form>
 
     <p v-if="error" class="form-error">{{ error }}</p>
diff --git a/src/inkwell/invites_api.py b/src/inkwell/invites_api.py
index 6305a77..211c200 100644
--- a/src/inkwell/invites_api.py
+++ b/src/inkwell/invites_api.py
@@ -11,16 +11,18 @@ from quart import Blueprint, g, jsonify, request
 from sqlalchemy import select
 from sqlalchemy.orm import aliased
 
-from . import audit
+from . import audit, mail_templates
 from .auth import require_admin
 from .common import normalize_email
 from .db import session_scope
 from .invites import MAX_DAYS, lifetime_days, serialize
+from .mailer import mail_settings, send
 from .models.invite import Invite
 from .models.user import User
 from .proxy import client_address
 from .responses import json_error, not_found, parse_uuid
 from .security import generate_token, hash_token
+from .settings import get_setting
 
 bp = Blueprint("invites", __name__, url_prefix="/api/invites")
 
@@ -38,10 +40,19 @@ async def create_invite():
     days = lifetime_days(data.get("days"))
     if days is None:
         return json_error(f"an invite lasts between 1 and {MAX_DAYS} days", 400)
+    # Emailing the link needs someone to send it to and a way to send. Both are
+    # checked BEFORE the invite exists, so a refusal leaves nothing half-made.
+    emailing = data.get("send_email") is True
+    if emailing and email is None:
+        return json_error("to email an invite, give the address it's for", 400)
 
     token = generate_token()
     now = datetime.now(timezone.utc)
     async with session_scope() as db:
+        cfg = await mail_settings(db) if emailing else None
+        if emailing and cfg is None:
+            return json_error("Email is off: set it up in Settings → Email first.", 400)
+        site = await get_setting(db, "site_name")
         invite = Invite(
             token_hash=hash_token(token),
             created_by=g.user_id,
@@ -59,9 +70,22 @@ async def create_invite():
     await audit.record(
         audit.INVITE_CREATED, user_id=g.user_id, email=admin.email, detail=f"for {email or 'anyone'}, {days} days"
     )
+    body: dict = {"invite": serialize(invite, now), "token": token}
+    if cfg is not None:
+        # Built from the public address, never from the request (mail_templates).
+        link = f"{cfg.public_url}/register?invite={token}"
+        try:
+            await send(cfg, email, mail_templates.invite(site, admin.display_name or admin.email, link, days))
+            body["emailed"] = True
+            logger.info("invite emailed id=%s to=%s", invite.id, email)
+        except Exception as e:  # any SMTP, socket or TLS failure; the admin needs its text
+            # The invite stands either way: the link is still shown once, so the admin
+            # can send it some other way.
+            logger.warning("invite email failed id=%s: %s", invite.id, e)
+            body["email_error"] = f"Couldn't send: {e}"
     # The token goes back exactly once. The client builds the link from it, since only
     # the browser knows the address people actually reach this server at.
-    return jsonify({"invite": serialize(invite, now), "token": token}), 201
+    return jsonify(body), 201
 
 
 @bp.get("")
diff --git a/src/inkwell/mail_templates.py b/src/inkwell/mail_templates.py
new file mode 100644
index 0000000..e77a20f
--- /dev/null
+++ b/src/inkwell/mail_templates.py
@@ -0,0 +1,150 @@
+"""What the server's emails say, and the one layout they all share (#5917).
+
+Each email is a function returning an `Email`: a subject, a plain-text part and an
+HTML part. `mailer.send` sends both as one multipart/alternative message, so a client
+that shows HTML gets the branded version and one that doesn't still gets every word
+and the link.
+
+The HTML is deliberately email-shaped rather than web-shaped. It uses tables and
+inline styles, because many mail clients drop `<style>` blocks and ignore flexbox.
+It uses no images or web fonts and fetches nothing: the app sends with no outbound
+network beyond the mail server (rule 164), and a remote image is a tracking pixel
+anyway. Everything taken from settings or from a person (the site name, an address,
+a link) is escaped before it goes into the HTML.
+
+Links come from Settings → General → Public address, never from the request: a
+forged Host header would otherwise mail a stranger a link to the forger's site.
+"""
+from __future__ import annotations
+
+from dataclasses import dataclass
+from html import escape
+
+# The brand yellow (`brand` in tailwind.config.js) and the app's neutral greys. The
+# button text is near-black for the same reason it is in the app: white on this
+# yellow is unreadable.
+BRAND = "#F5C518"
+INK = "#171717"
+MUTED = "#737373"
+RULE = "#E5E5E5"
+PAGE = "#F5F5F5"
+
+
+@dataclass(frozen=True)
+class Email:
+    subject: str
+    text: str
+    html: str
+
+
+@dataclass(frozen=True)
+class _Button:
+    label: str
+    url: str
+
+
+def _render(
+    site: str, subject: str, heading: str, lines: list[str], button: _Button | None, footer: str
+) -> Email:
+    """One email in the shared layout: the site's name, a heading, the message, a
+    button for the link, and a footer saying who sent it and why (preference 194).
+
+    `lines` are paragraphs of plain text. The button goes after the first one, and the
+    text part spells its link out in full, since that is the only way a text-only
+    client can follow it.
+    """
+    text_parts = [heading] + ([lines[0]] if lines else [])
+    if button:
+        text_parts.append(f"{button.label}:\n{button.url}")
+    text_parts.extend(lines[1:])
+    text = "\n\n".join(text_parts) + f"\n\n-- \n{footer}\n"
+
+    paragraphs = [
+        f'<p style="margin:0 0 16px;font-size:15px;line-height:1.55;color:{INK}">{escape(line)}</p>'
+        for line in lines
+    ]
+    if button:
+        url = escape(button.url, quote=True)
+        action = (
+            '<table role="presentation" cellpadding="0" cellspacing="0" style="margin:8px 0 24px">'
+            f'<tr><td style="border-radius:8px;background:{BRAND}">'
+            f'<a href="{url}" style="display:inline-block;padding:12px 22px;font-size:15px;'
+            f'font-weight:600;color:{INK};text-decoration:none;border-radius:8px">{escape(button.label)}</a>'
+            "</td></tr></table>"
+            f'<p style="margin:0 0 16px;font-size:12px;line-height:1.5;color:{MUTED}">'
+            f'If the button doesn\'t work, paste this address into your browser:<br>'
+            f'<a href="{url}" style="color:{MUTED};word-break:break-all">{escape(button.url)}</a></p>'
+        )
+        paragraphs.insert(1 if paragraphs else 0, action)
+
+    html = (
+        "<!doctype html>"
+        f'<html><head><meta charset="utf-8"><meta name="viewport" content="width=device-width">'
+        f"<title>{escape(subject)}</title></head>"
+        f'<body style="margin:0;padding:0;background:{PAGE}">'
+        f'<table role="presentation" width="100%" cellpadding="0" cellspacing="0" style="background:{PAGE}">'
+        '<tr><td align="center" style="padding:32px 16px">'
+        '<table role="presentation" width="100%" cellpadding="0" cellspacing="0" '
+        'style="max-width:520px;background:#FFFFFF;border-radius:12px;'
+        f'border:1px solid {RULE};font-family:-apple-system,Segoe UI,Roboto,Helvetica,Arial,sans-serif">'
+        f'<tr><td style="padding:20px 28px;border-bottom:1px solid {RULE}">'
+        f'<span style="display:inline-block;width:10px;height:10px;border-radius:5px;background:{BRAND};'
+        'margin-right:8px;vertical-align:middle"></span>'
+        f'<span style="font-size:15px;font-weight:700;color:{INK};vertical-align:middle">{escape(site)}</span>'
+        "</td></tr>"
+        f'<tr><td style="padding:28px">'
+        f'<h1 style="margin:0 0 16px;font-size:20px;line-height:1.3;font-weight:700;color:{INK}">'
+        f"{escape(heading)}</h1>"
+        f'{"".join(paragraphs)}</td></tr>'
+        f'<tr><td style="padding:16px 28px;border-top:1px solid {RULE};font-size:12px;line-height:1.5;'
+        f'color:{MUTED}">{escape(footer)}</td></tr>'
+        "</table></td></tr></table></body></html>"
+    )
+    return Email(subject=subject, text=text, html=html)
+
+
+def password_reset(site: str, to: str, link: str) -> Email:
+    return _render(
+        site,
+        f"Reset your {site} password",
+        "Reset your password",
+        [
+            f"Someone asked to reset the password for {to} on {site}. If it was you, "
+            "choose a new one within the hour.",
+            "Setting it signs you out everywhere else. If it wasn't you, ignore this "
+            "email and your password stays as it is.",
+        ],
+        _Button("Choose a new password", link),
+        f"Sent by {site} because a password reset was asked for on this address.",
+    )
+
+
+def test_message(site: str, public_url: str) -> Email:
+    return _render(
+        site,
+        f"{site} test email",
+        "Email works",
+        [
+            f"This is a test from {site} at {public_url}.",
+            "Password reset and invite emails will arrive looking like this one.",
+        ],
+        None,
+        f"Sent by {site} because an admin pressed Send a test email.",
+    )
+
+
+def invite(site: str, inviter: str, link: str, days: int) -> Email:
+    when = "within a day" if days == 1 else f"within {days} days"
+    return _render(
+        site,
+        f"{inviter} invited you to {site}",
+        f"You're invited to {site}",
+        [
+            f"{inviter} invited you to make an account on {site}, a place to keep notes. "
+            f"The link works once, and only {when}.",
+            "If you weren't expecting this, you can ignore it. Nothing happens unless "
+            "the link is used.",
+        ],
+        _Button("Make your account", link),
+        f"Sent by {site} on behalf of {inviter}.",
+    )
diff --git a/src/inkwell/mailer.py b/src/inkwell/mailer.py
index 57fd665..98dfa51 100644
--- a/src/inkwell/mailer.py
+++ b/src/inkwell/mailer.py
@@ -1,6 +1,7 @@
 """Sending email over the SMTP server set in Settings → Email (#5266).
 
-Used for password reset links, and for the admin's test message. Email is an optional
+Used for password reset links, invites, and the admin's test message. What each one
+says is in `mail_templates`; this module only delivers. Email is an optional
 feature (rule 164): with no server set, `mail_settings` answers None and everything
 that would send says it is not available. A send that fails is logged and never
 takes anything else down with it.
@@ -18,6 +19,7 @@ from dataclasses import dataclass
 from email.message import EmailMessage
 
 from .common import detach
+from .mail_templates import Email
 from .settings import get_setting, mail_configured
 
 logger = logging.getLogger(__name__)
@@ -53,12 +55,15 @@ async def mail_settings(db) -> MailSettings | None:
     )
 
 
-def build_message(cfg: MailSettings, to: str, subject: str, text: str) -> EmailMessage:
+def build_message(cfg: MailSettings, to: str, email: Email) -> EmailMessage:
+    """multipart/alternative: the text part first, the HTML part last, so a client
+    picks the HTML when it can and the text when it can't."""
     msg = EmailMessage()
     msg["From"] = cfg.sender
     msg["To"] = to
-    msg["Subject"] = subject
-    msg.set_content(text)
+    msg["Subject"] = email.subject
+    msg.set_content(email.text)
+    msg.add_alternative(email.html, subtype="html")
     return msg
 
 
@@ -77,9 +82,9 @@ def _deliver(cfg: MailSettings, msg: EmailMessage) -> None:
         server.send_message(msg)
 
 
-async def send(cfg: MailSettings, to: str, subject: str, text: str) -> None:
-    """Send one plain-text email. Raises when the server refuses or can't be reached."""
-    await asyncio.to_thread(_deliver, cfg, build_message(cfg, to, subject, text))
+async def send(cfg: MailSettings, to: str, email: Email) -> None:
+    """Send one email. Raises when the server refuses or can't be reached."""
+    await asyncio.to_thread(_deliver, cfg, build_message(cfg, to, email))
 
 
 # Sends started by `send_later`, held so they aren't collected mid-flight.
diff --git a/src/inkwell/password_resets.py b/src/inkwell/password_resets.py
index 3f46219..31faa11 100644
--- a/src/inkwell/password_resets.py
+++ b/src/inkwell/password_resets.py
@@ -22,6 +22,7 @@ from datetime import datetime, timedelta, timezone
 from sqlalchemy import delete, select, update
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from . import mail_templates
 from .db import session_scope
 from .mailer import mail_settings, send
 from .models.password_reset import PasswordReset
@@ -94,15 +95,7 @@ async def mail_reset_link(email: str) -> None:
             site = await get_setting(db, "site_name")
             to = user.email
         link = f"{cfg.public_url}/reset-password?token={token}"
-        await send(
-            cfg,
-            to,
-            f"Reset your {site} password",
-            f"Someone asked to reset the password for {to} on {site}.\n\n"
-            f"If it was you, open this link within the hour to choose a new one:\n\n{link}\n\n"
-            "Setting it signs you out everywhere else. If it wasn't you, ignore this "
-            "email and your password stays as it is.\n",
-        )
+        await send(cfg, to, mail_templates.password_reset(site, to, link))
         logger.info("password reset email sent to=%s", to)
     except Exception:
         logger.exception("password reset email failed for=%s", email)
diff --git a/src/inkwell/settings_api.py b/src/inkwell/settings_api.py
index d0fc08b..57a5d73 100644
--- a/src/inkwell/settings_api.py
+++ b/src/inkwell/settings_api.py
@@ -6,6 +6,7 @@ from quart import Blueprint, current_app, g, jsonify, request
 
 from .auth import require_admin
 from .db import session_scope
+from . import mail_templates
 from .mailer import mail_settings, send
 from .responses import json_error
 from .models.user import User
@@ -66,12 +67,7 @@ async def test_email():
         admin = await db.get(User, g.user_id)
         site = await get_setting(db, "site_name")
     try:
-        await send(
-            cfg,
-            admin.email,
-            f"{site} test email",
-            f"This is a test from {site} at {cfg.public_url}. Password reset emails will arrive like this one.\n",
-        )
+        await send(cfg, admin.email, mail_templates.test_message(site, cfg.public_url))
     except Exception as e:  # any SMTP, socket or TLS failure; the admin needs its text
         logger.warning("test email failed: %s", e)
         return json_error(f"Couldn't send: {e}", 502)
diff --git a/tests/test_integration.py b/tests/test_integration.py
index d31d500..2560437 100644
--- a/tests/test_integration.py
+++ b/tests/test_integration.py
@@ -2029,7 +2029,8 @@ async def test_a_forgotten_password_is_reset_from_an_emailed_link(app_client, db
     await mailer.drain()
 
     assert [m["To"] for m in outbox] == ["guest@example.test"]
-    text = outbox[0].get_content()
+    text = outbox[0].get_body(preferencelist=("plain",)).get_content()
+    assert "reset-password?token=" in outbox[0].get_body(preferencelist=("html",)).get_content()
     link = re.search(r"https://notes\.example\.test/reset-password\?token=([\w-]+)", text)
     assert link, text
     async with session_scope() as fresh:
@@ -2055,6 +2056,31 @@ async def test_reset_emails_stop_at_the_cap_without_saying_so(app_client, db, mo
     assert len(outbox) == 3  # reset_emails_per_account defaults to 3
 
 
+async def test_an_invite_is_emailed_to_its_address_with_a_working_link(app_client, db, monkeypatch):
+    await _mail_off()
+    outbox = _outbox(monkeypatch)
+    await _admin_with_invite(app_client)
+
+    # Refused, and nothing made, while email is off or there is no one to send to.
+    off = await app_client.post("/api/invites", json={"email": "friend@example.test", "send_email": True})
+    assert off.status_code == 400
+    await app_client.patch("/api/settings", json=_MAIL_SETTINGS)
+    nobody = await app_client.post("/api/invites", json={"send_email": True})
+    assert nobody.status_code == 400
+
+    made = await app_client.post("/api/invites", json={"email": "friend@example.test", "days": 7, "send_email": True})
+    assert made.status_code == 201
+    body = await made.get_json()
+    assert body["emailed"] is True
+    assert [m["To"] for m in outbox] == ["friend@example.test"]
+    text = outbox[0].get_body(preferencelist=("plain",)).get_content()
+    assert f"https://notes.example.test/register?invite={body['token']}" in text
+    assert "within 7 days" in text
+
+    registered = await _register("friend@example.test", body["token"])
+    assert registered.status_code == 201
+
+
 async def test_the_test_email_goes_to_the_admin_and_reports_a_failure(app_client, db, monkeypatch):
     await _mail_off()
     outbox = _outbox(monkeypatch)
diff --git a/tests/test_mail_templates.py b/tests/test_mail_templates.py
new file mode 100644
index 0000000..d8123bb
--- /dev/null
+++ b/tests/test_mail_templates.py
@@ -0,0 +1,43 @@
+from email import message_from_bytes
+from email.policy import default
+
+from inkwell import mail_templates
+from inkwell.mailer import MailSettings, build_message
+
+LINK = "https://notes.example.test/reset-password?token=abc-123"
+
+
+def test_every_email_carries_its_link_in_both_parts():
+    for email in (
+        mail_templates.password_reset("Inkwell", "a@example.test", LINK),
+        mail_templates.invite("Inkwell", "Sam", LINK, 7),
+    ):
+        assert LINK in email.text
+        assert f'href="{LINK}"' in email.html
+
+
+def test_text_from_settings_and_people_is_escaped_in_the_html():
+    email = mail_templates.invite('<b>Ink</b> & "co"', "<script>x</script>", LINK, 1)
+    assert "<script>" not in email.html
+    assert "&lt;b&gt;Ink&lt;/b&gt; &amp;" in email.html
+    # The text part is plain text, so it is left as written.
+    assert "<script>x</script>" in email.text
+    assert "within a day" in email.text
+
+
+def test_the_html_fetches_nothing():
+    """No remote images or fonts: the app sends with no outbound network, and a remote
+    image in an email is a tracking pixel."""
+    html = mail_templates.password_reset("Inkwell", "a@example.test", LINK).html
+    assert "<img" not in html
+    assert "src=" not in html
+    assert "@import" not in html
+
+
+def test_the_message_is_text_first_then_html():
+    cfg = MailSettings("smtp.example.test", 587, "starttls", "", "", "inkwell@example.test", "https://x")
+    msg = build_message(cfg, "a@example.test", mail_templates.test_message("Inkwell", "https://x"))
+    parsed = message_from_bytes(msg.as_bytes(), policy=default)
+    assert parsed.get_content_type() == "multipart/alternative"
+    assert [p.get_content_type() for p in parsed.iter_parts()] == ["text/plain", "text/html"]
+    assert parsed["Subject"] == "Inkwell test email"