diff --git a/migrations/pg/2026-04-17_suppression-list-hashed.sql b/migrations/pg/2026-04-17_suppression-list-hashed.sql
new file mode 100644
index 0000000..5e6706a
--- /dev/null
+++ b/migrations/pg/2026-04-17_suppression-list-hashed.sql
@@ -0,0 +1,13 @@
+-- Schritt 1: Hash-Spalte hinzufügen (additiv, kein Breaking Change)
+ALTER TABLE suppression_list ADD COLUMN IF NOT EXISTS email_hash TEXT;
+
+CREATE INDEX IF NOT EXISTS idx_suppression_list_email_hash ON suppression_list(email_hash);
+
+-- Schritt 2: Bestehende Einträge hashen (PostgreSQL-native SHA256)
+UPDATE suppression_list
+  SET email_hash = encode(sha256(lower(trim(email))::bytea), 'hex')
+  WHERE email_hash IS NULL;
+
+-- Schritt 3 (nach Validierung separat ausführen):
+-- ALTER TABLE suppression_list ALTER COLUMN email_hash SET NOT NULL;
+-- ALTER TABLE suppression_list DROP COLUMN email;
diff --git a/src/server/suppression/check.test.ts b/src/server/suppression/check.test.ts
index edb6dd6..fc03a95 100644
--- a/src/server/suppression/check.test.ts
+++ b/src/server/suppression/check.test.ts
@@ -12,7 +12,7 @@ vi.mock('../db/tenant', () => ({
 import { checkSuppression } from './check'
 
 describe('checkSuppression', () => {
-  beforeEach(() => vi.clearAllMocks())
+  beforeEach(() => mockClient.query.mockReset())
 
   it('gibt true zurück wenn E-Mail in Suppression-Liste', async () => {
     mockClient.query.mockResolvedValueOnce([{ exists: true }])
@@ -26,21 +26,41 @@ describe('checkSuppression', () => {
     expect(result).toBe(false)
   })
 
-  it('normalisiert E-Mail (lowercase + trim) vor dem Check', async () => {
+  it('sucht per SHA256-Hash, nicht per Klartext-E-Mail', async () => {
+    mockClient.query.mockResolvedValueOnce([])
+    await checkSuppression('tenant1', 'Test@Example.com')
+    const [sql, params] = mockClient.query.mock.calls[0] as [string, string[]]
+    expect(sql).toContain('email_hash')
+    expect(sql).not.toContain('email =')
+    // SHA256-Hex ist 64 Zeichen
+    expect(params[0]).toMatch(/^[a-f0-9]{64}$/)
+  })
+
+  it('normalisiert E-Mail vor dem Hashing (lowercase + trim)', async () => {
     mockClient.query.mockResolvedValueOnce([])
     await checkSuppression('tenant1', '  TEST@EXAMPLE.COM  ')
-    expect(mockClient.query).toHaveBeenCalledWith(
-      expect.any(String),
-      ['test@example.com']
-    )
+
+    mockClient.query.mockResolvedValueOnce([])
+    await checkSuppression('tenant1', 'test@example.com')
+
+    const hash1 = (mockClient.query.mock.calls[0] as [string, string[]])[1][0]
+    const hash2 = (mockClient.query.mock.calls[1] as [string, string[]])[1][0]
+    expect(hash1).toBe(hash2)
   })
 
   it('Query ist parametrisiert (kein String-Interpolation)', async () => {
     mockClient.query.mockResolvedValueOnce([])
     await checkSuppression('tenant1', 'x@x.com')
-    const call = mockClient.query.mock.calls[0]
+    const call = mockClient.query.mock.calls[0] as [string, string[]]
     expect(call[0]).toContain('$1')
-    expect(call[1]).toEqual(['x@x.com'])
+    expect(call[1]).toHaveLength(1)
+  })
+
+  it('sendet nie die Klartext-E-Mail an die Datenbank', async () => {
+    mockClient.query.mockResolvedValueOnce([])
+    await checkSuppression('tenant1', 'secret@example.com')
+    const [, params] = mockClient.query.mock.calls[0] as [string, string[]]
+    expect(params[0]).not.toContain('secret@example.com')
   })
 
   it('propagiert Fehler bei ungültiger tenantId nach oben', async () => {
diff --git a/src/server/suppression/check.ts b/src/server/suppression/check.ts
index 4185596..e1916d6 100644
--- a/src/server/suppression/check.ts
+++ b/src/server/suppression/check.ts
@@ -1,11 +1,12 @@
 import { withTenant } from '../db/tenant'
+import { hashEmail } from '../../lib/crypto'
 
 export async function checkSuppression(tenantId: string, email: string): Promise<boolean> {
-  const normalized = email.toLowerCase().trim()
+  const hash = hashEmail(email)
   const rows = await withTenant(tenantId, (client) =>
     client.query<{ '?column?': number }>(
-      'SELECT 1 FROM suppression_list WHERE email = $1 LIMIT 1',
-      [normalized]
+      'SELECT 1 FROM suppression_list WHERE email_hash = $1 LIMIT 1',
+      [hash]
     )
   )
   return rows.length > 0