diff --git a/frontend/src/client/i18n.ts b/frontend/src/client/i18n.ts
index 2053da3..0520764 100644
--- a/frontend/src/client/i18n.ts
+++ b/frontend/src/client/i18n.ts
@@ -1595,6 +1595,14 @@ const translations: Record<Lang, Record<string, string>> = {
     "projects.detail.team.invite.hint": "Benutzer nicht gefunden?",
     "projects.detail.team.invite.hint_email": "Niemand mit dieser E-Mail.",
     "projects.detail.team.invite.cta": "Einladen",
+    // t-paliad-231 — pure-client mailto: button on the Team tab. No
+    // server call; opens the local mail client with every selected
+    // member queued in the To: line.
+    "projects.team.mailto.label": "Mail an Auswahl",
+    "projects.team.mailto.empty": "Mindestens ein Mitglied auswählen",
+    "projects.team.mailto.count": "{n} ausgewählt",
+    "projects.team.mailto.select_all": "Alle sichtbaren auswählen",
+    "projects.team.mailto.select_row": "Mitglied auswählen",
     "projects.view.tree": "Baumansicht",
     "projects.tree.toggle": "Aufklappen / Zuklappen",
     "projects.tree.loading": "Baum wird geladen\u2026",
@@ -4449,6 +4457,12 @@ const translations: Record<Lang, Record<string, string>> = {
     "projects.detail.team.invite.hint": "User not found?",
     "projects.detail.team.invite.hint_email": "No one with that email.",
     "projects.detail.team.invite.cta": "Invite",
+    // t-paliad-231 — pure-client mailto: button on the Team tab.
+    "projects.team.mailto.label": "Mail to selection",
+    "projects.team.mailto.empty": "Select at least one member",
+    "projects.team.mailto.count": "{n} selected",
+    "projects.team.mailto.select_all": "Select all visible",
+    "projects.team.mailto.select_row": "Select member",
     "projects.view.tree": "Tree view",
     "projects.tree.toggle": "Expand / collapse",
     "projects.tree.loading": "Loading tree…",
diff --git a/frontend/src/client/projects-detail.ts b/frontend/src/client/projects-detail.ts
index 1acb8b0..e6879d4 100644
--- a/frontend/src/client/projects-detail.ts
+++ b/frontend/src/client/projects-detail.ts
@@ -13,6 +13,7 @@ import { mountFilterBar, type BarHandle } from "./filter-bar";
 import type { FilterSpec, RenderSpec } from "./views/types";
 import { renderSmartTimeline, type TimelineEvent as SmartTimelineEvent, type LaneInfo as SmartTimelineLane } from "./views/shape-timeline";
 import { loadAndRenderSubmissions } from "./submissions";
+import { buildMailtoHref, type BroadcastRecipient } from "./broadcast";
 
 interface Project {
   id: string;
@@ -236,6 +237,12 @@ let attachedUnits: AttachedUnit[] = [];
 let allUnits: { id: string; name: string; office: string }[] = [];
 let userOptions: { id: string; display_name: string; email: string; profession?: string }[] = [];
 
+// t-paliad-231 — checkbox selection backing the "Mail an Auswahl"
+// mailto: button on the Team tab. Pure client state, wiped on page
+// navigation. Pruned to currently-visible user_ids on every renderTeam
+// so removed/filtered-out members don't ride along in the next mailto.
+const selectedMailUserIDs: Set<string> = new Set();
+
 const EVENTS_PAGE_SIZE = 50;
 let eventsHasMore = false;
 let eventsLoadingMore = false;
@@ -2507,6 +2514,7 @@ async function loadUserList() {
 function renderTeam() {
   const body = document.getElementById("team-body")!;
   const empty = document.getElementById("team-empty")!;
+  const mailtoControls = document.getElementById("team-mailto-controls") as HTMLDivElement | null;
 
   // Existing team-body shows the direct + ancestor-inherited members
   // returned by /api/projects/{id}/team. The derived + descendant
@@ -2517,12 +2525,21 @@ function renderTeam() {
   if (totalRows === 0) {
     body.innerHTML = "";
     empty.style.display = "";
+    if (mailtoControls) mailtoControls.style.display = "none";
+    selectedMailUserIDs.clear();
+    syncMailtoButton();
+    syncMasterCheckbox();
     renderDescendantStaffed();
     renderDerivedMembers();
     renderAttachedUnits();
     return;
   }
   empty.style.display = "none";
+  if (mailtoControls) mailtoControls.style.display = teamMembers.length > 0 ? "" : "none";
+  // Prune the selection to whoever is actually rendered in team-body
+  // right now (e.g. a member just got removed). Invariant: selection ⊆
+  // currently-visible team-body rows.
+  pruneMailSelectionToVisible();
 
   // t-paliad-223: callers with effective_project_admin authority see an
   // inline <select> on the Rolle cell. Everyone else sees the read-only
@@ -2563,7 +2580,17 @@ function renderTeam() {
           ? renderResponsibilitySelect(m.user_id, responsibility)
           : `<span class="projekt-team-responsibility">${esc(responsibilityLabel)}</span>`;
 
+      // t-paliad-231: per-row checkbox feeding selectedMailUserIDs. Only
+      // rows with a real email participate in the mailto: build; rows
+      // without are still rendered with a disabled checkbox so the
+      // column geometry stays uniform.
+      const hasEmail = !!(m.user_email && m.user_email.trim());
+      const checked = hasEmail && selectedMailUserIDs.has(m.user_id) ? " checked" : "";
+      const disabled = hasEmail ? "" : " disabled";
+      const checkboxCell = `<td class="team-col-select"><input type="checkbox" class="team-mail-select" data-user-id="${esc(m.user_id)}" data-email="${escAttr(m.user_email || "")}" aria-label="${escAttr(t("projects.team.mailto.select_row") || "Mitglied auswählen")}"${checked}${disabled} /></td>`;
+
       return `<tr>
+        ${checkboxCell}
         <td><strong>${esc(m.user_display_name || m.user_email)}</strong>
             <span class="form-hint">&middot; ${esc(m.user_email)}${officeLabel ? " &middot; " + esc(officeLabel) : ""}</span></td>
         <td><span class="${profCls}" title="${escAttr(professionTitle)}">${esc(professionLabel)}</span></td>
@@ -2574,6 +2601,21 @@ function renderTeam() {
     })
     .join("");
 
+  // t-paliad-231 — wire row checkboxes + master + mailto button.
+  body.querySelectorAll<HTMLInputElement>(".team-mail-select").forEach((cb) => {
+    cb.addEventListener("change", () => {
+      const userID = cb.dataset.userId!;
+      if (cb.checked) selectedMailUserIDs.add(userID);
+      else selectedMailUserIDs.delete(userID);
+      syncMailtoButton();
+      syncMasterCheckbox();
+    });
+  });
+  wireMailtoMaster();
+  wireMailtoButton();
+  syncMailtoButton();
+  syncMasterCheckbox();
+
   body.querySelectorAll<HTMLButtonElement>(".team-remove-btn").forEach((btn) => {
     btn.addEventListener("click", async () => {
       if (!project) return;
@@ -2860,6 +2902,113 @@ async function showTeamErrorToast(resp: Response): Promise<void> {
   }, 5000);
 }
 
+// t-paliad-231 — mailto: selection helpers for the Team tab. The
+// admin-only server SMTP broadcast (POST /api/team/broadcast) lives
+// elsewhere; this is the non-admin / quick-CC variant that opens the
+// user's local mail client. Pure client; no server call.
+function pruneMailSelectionToVisible(): void {
+  const visible = new Set<string>();
+  for (const m of teamMembers) {
+    if (m.user_email && m.user_email.trim()) visible.add(m.user_id);
+  }
+  for (const id of Array.from(selectedMailUserIDs)) {
+    if (!visible.has(id)) selectedMailUserIDs.delete(id);
+  }
+}
+
+function selectedMailRecipients(): BroadcastRecipient[] {
+  const out: BroadcastRecipient[] = [];
+  for (const m of teamMembers) {
+    if (!selectedMailUserIDs.has(m.user_id)) continue;
+    if (!m.user_email || !m.user_email.trim()) continue;
+    out.push({
+      user_id: m.user_id,
+      email: m.user_email,
+      display_name: m.user_display_name || m.user_email,
+      first_name: (m.user_display_name || m.user_email).trim().split(/\s+/)[0] ?? "",
+      role_on_project: m.responsibility || "member",
+    });
+  }
+  return out;
+}
+
+function syncMailtoButton(): void {
+  const btn = document.getElementById("team-mailto-btn") as HTMLButtonElement | null;
+  const label = document.getElementById("team-mailto-label") as HTMLSpanElement | null;
+  if (!btn || !label) return;
+  const n = selectedMailRecipients().length;
+  const baseLabel = t("projects.team.mailto.label") || "Mail an Auswahl";
+  if (n === 0) {
+    btn.disabled = true;
+    label.textContent = baseLabel;
+    btn.title = t("projects.team.mailto.empty") || "Mindestens ein Mitglied auswählen";
+  } else {
+    btn.disabled = false;
+    label.textContent = `${baseLabel} (${n})`;
+    const tooltip = (t("projects.team.mailto.count") || "{n} ausgewählt").replace("{n}", String(n));
+    btn.title = tooltip;
+  }
+}
+
+function syncMasterCheckbox(): void {
+  const master = document.getElementById("team-select-master") as HTMLInputElement | null;
+  if (!master) return;
+  // Only count rows that actually rendered with an enabled checkbox —
+  // members without an email don't participate.
+  const checkboxes = document.querySelectorAll<HTMLInputElement>(
+    "#team-body .team-mail-select:not(:disabled)",
+  );
+  const total = checkboxes.length;
+  let selected = 0;
+  checkboxes.forEach((cb) => {
+    if (selectedMailUserIDs.has(cb.dataset.userId!)) selected++;
+  });
+  master.disabled = total === 0;
+  if (total === 0 || selected === 0) {
+    master.checked = false;
+    master.indeterminate = false;
+  } else if (selected === total) {
+    master.checked = true;
+    master.indeterminate = false;
+  } else {
+    master.checked = false;
+    master.indeterminate = true;
+  }
+}
+
+// wireMailtoMaster is idempotent — registers once via a sentinel data
+// attr so re-renders don't stack click handlers.
+function wireMailtoMaster(): void {
+  const master = document.getElementById("team-select-master") as HTMLInputElement | null;
+  if (!master || master.dataset.wired === "1") return;
+  master.dataset.wired = "1";
+  master.addEventListener("change", () => {
+    const turnOn = master.checked;
+    document
+      .querySelectorAll<HTMLInputElement>("#team-body .team-mail-select:not(:disabled)")
+      .forEach((cb) => {
+        const id = cb.dataset.userId!;
+        if (turnOn) selectedMailUserIDs.add(id);
+        else selectedMailUserIDs.delete(id);
+        cb.checked = turnOn;
+      });
+    syncMailtoButton();
+    syncMasterCheckbox();
+  });
+}
+
+function wireMailtoButton(): void {
+  const btn = document.getElementById("team-mailto-btn") as HTMLButtonElement | null;
+  if (!btn || btn.dataset.wired === "1") return;
+  btn.dataset.wired = "1";
+  btn.addEventListener("click", (e) => {
+    e.preventDefault();
+    const recipients = selectedMailRecipients();
+    if (recipients.length === 0) return;
+    window.location.href = buildMailtoHref(recipients);
+  });
+}
+
 function initTeamForm(id: string) {
   const addBtn = document.getElementById("team-add-btn") as HTMLButtonElement | null;
   const form = document.getElementById("team-form") as HTMLFormElement | null;
diff --git a/frontend/src/i18n-keys.ts b/frontend/src/i18n-keys.ts
index 0084fbd..3d1cd7a 100644
--- a/frontend/src/i18n-keys.ts
+++ b/frontend/src/i18n-keys.ts
@@ -2399,6 +2399,11 @@ export type I18nKey =
   | "projects.team.error.generic"
   | "projects.team.error.last_admin"
   | "projects.team.inherited.hint"
+  | "projects.team.mailto.count"
+  | "projects.team.mailto.empty"
+  | "projects.team.mailto.label"
+  | "projects.team.mailto.select_all"
+  | "projects.team.mailto.select_row"
   | "projects.team.profession.associate"
   | "projects.team.profession.hint"
   | "projects.team.profession.none"
diff --git a/frontend/src/projects-detail.tsx b/frontend/src/projects-detail.tsx
index 867ae7c..8f90f02 100644
--- a/frontend/src/projects-detail.tsx
+++ b/frontend/src/projects-detail.tsx
@@ -286,9 +286,33 @@ export function renderProjectsDetail(): string {
                     <p className="form-msg" id="team-msg" />
                   </form>
 
+                  {/* t-paliad-231 — pure-client mailto: for non-admins.
+                      Button stays disabled until at least one row is
+                      selected; click opens a mailto: with every selected
+                      member in the To: line. No server call. */}
+                  <div className="party-controls team-mailto-controls" id="team-mailto-controls" style="display:none">
+                    <button
+                      type="button"
+                      id="team-mailto-btn"
+                      className="btn-secondary btn-small"
+                      disabled
+                      data-i18n-title="projects.team.mailto.empty"
+                      title="Mindestens ein Mitglied ausw&auml;hlen"
+                    >
+                      <span id="team-mailto-label" data-i18n="projects.team.mailto.label">Mail an Auswahl</span>
+                    </button>
+                  </div>
+
                   <table className="party-table">
                     <thead>
                       <tr>
+                        <th className="team-col-select">
+                          <input
+                            type="checkbox"
+                            id="team-select-master"
+                            aria-label="Alle sichtbaren ausw&auml;hlen"
+                          />
+                        </th>
                         <th data-i18n="projects.detail.team.col.name">Name</th>
                         <th data-i18n="projects.detail.team.col.profession">Profession</th>
                         <th data-i18n="projects.detail.team.col.responsibility">Rolle</th>
diff --git a/frontend/src/styles/global.css b/frontend/src/styles/global.css
index 7809c0f..085f3b0 100644
--- a/frontend/src/styles/global.css
+++ b/frontend/src/styles/global.css
@@ -7143,6 +7143,31 @@ dialog.modal::backdrop {
     border-bottom: none;
 }
 
+/* t-paliad-231 — checkbox column for the project-detail Team tab's
+   "Mail an Auswahl" mailto: selection. Narrow, centred, accent-coloured. */
+.party-table .team-col-select {
+    width: 2.4rem;
+    text-align: center;
+    padding-left: 0.6rem;
+    padding-right: 0.4rem;
+}
+
+.team-mail-select,
+#team-select-master {
+    accent-color: var(--color-primary, #c6f41c);
+    cursor: pointer;
+}
+
+.team-mail-select:disabled {
+    cursor: not-allowed;
+    opacity: 0.4;
+}
+
+.team-mailto-controls {
+    justify-content: flex-end;
+    margin-bottom: 0.5rem;
+}
+
 .entity-col-actions {
     text-align: right;
 }