diff --git a/application/routes.py b/application/routes.py
index da1e560..702bf03 100644
--- a/application/routes.py
+++ b/application/routes.py
@@ -4,6 +4,19 @@ from .models import Adresse, Frage, Antwort
 from utils import generate_vcard
 import re
 
+# Prefer robust validators when available; fall back to simple checks.
+try:
+    from email_validator import validate_email, EmailNotValidError
+except Exception:
+    validate_email = None
+    EmailNotValidError = Exception
+
+try:
+    import phonenumbers
+except Exception:
+    phonenumbers = None
+
+
 bp = Blueprint('public', __name__)
 
 
@@ -22,14 +35,51 @@ def index():
         email = request.form.get('email', '').strip()
 
         errors = {}
-        email_re = re.compile(r"[^@]+@[^@]+\.[^@]+")
+
+        # Email validation: use `email_validator` if present, else fallback regex
         if email:
-            if not email_re.match(email):
-                errors['email'] = 'Ungültige E-Mail-Adresse'
+            if validate_email:
+                try:
+                    # disable deliverability checks (MX/DNS) to avoid rejecting
+                    # addresses like max@example.com during testing
+                    valid = validate_email(email, check_deliverability=False)
+                    email = valid.email
+                except EmailNotValidError:
+                    errors['email'] = 'Ungültige E-Mail-Adresse'
+            else:
+                email_re = re.compile(r"[^@]+@[^@]+\.[^@]+")
+                if not email_re.match(email):
+                    errors['email'] = 'Ungültige E-Mail-Adresse'
+
+        # German PLZ: exactly 5 digits
         if plz:
-            if not re.fullmatch(r"\d{5}", plz):
+            if not plz.isdigit() or len(plz) != 5:
                 errors['plz'] = 'Postleitzahl muss genau 5 Ziffern haben'
 
+        # Phone validation: require both country code and number when provided
+        if telefon_vorwahl or telefon_nummer:
+            if not (telefon_vorwahl and telefon_nummer):
+                errors['telefon'] = 'Vorwahl und Telefonnummer müssen beide angegeben werden'
+            else:
+                if phonenumbers:
+                    raw = telefon_vorwahl.lstrip('+') + telefon_nummer
+                    international = '+' + raw
+                    try:
+                        parsed = phonenumbers.parse(international, None)
+                        is_valid = phonenumbers.is_valid_number(parsed)
+                    except Exception:
+                        is_valid = False
+                    # if phonenumbers says invalid, fall back to a simple heuristic
+                    if not is_valid:
+                        if not (telefon_vorwahl.lstrip('+').isdigit() and telefon_nummer.isdigit()) or len(telefon_nummer) < 3:
+                            errors['telefon'] = 'Ungültige Telefonnummer'
+                else:
+                    # fallback: basic numeric checks
+                    if not (telefon_vorwahl.lstrip('+').isdigit() and telefon_nummer.isdigit()):
+                        errors['telefon'] = 'Ungültige Telefonnummer'
+                    elif len(telefon_nummer) < 3:
+                        errors['telefon'] = 'Ungültige Telefonnummer'
+
         if errors:
             fragen = Frage.query.all()
             form = request.form.to_dict()
@@ -61,8 +111,8 @@ def index():
         try:
             base_dir = current_app.config.get('BASE_DIR') if current_app.config.get('BASE_DIR') else getattr(current_app, 'BASE_DIR', '.')
             generate_vcard(adresse, base_dir)
-        except Exception as e:
-            current_app.logger.exception('Fehler beim Erzeugen der vCard for adresse id=%s: %s', adresse.id if hasattr(adresse, 'id') else 'unknown', e)
+        except Exception:
+            current_app.logger.exception('Fehler beim Erzeugen der vCard for adresse id=%s', adresse.id if hasattr(adresse, 'id') else 'unknown')
 
         return redirect(url_for('public.danke', id=adresse.id))
 
@@ -72,6 +122,6 @@ def index():
 
 @bp.route('/danke')
 def danke():
-    id = request.args.get('id')
-    adresse = db.session.get(Adresse, int(id)) if id else None
+    ad_id = request.args.get('id')
+    adresse = db.session.get(Adresse, int(ad_id)) if ad_id else None
     return render_template('danke.html', adresse=adresse)
diff --git a/application/routes_fixed.py b/application/routes_fixed.py
new file mode 100644
index 0000000..59c3ecf
--- /dev/null
+++ b/application/routes_fixed.py
@@ -0,0 +1,124 @@
+from flask import Blueprint, render_template, request, redirect, url_for, current_app
+from .extensions import db
+from .models import Adresse, Frage, Antwort
+from utils import generate_vcard
+import re
+
+# Prefer robust validators when available; fall back to simple checks.
+try:
+    from email_validator import validate_email, EmailNotValidError
+except Exception:
+    validate_email = None
+    EmailNotValidError = Exception
+
+try:
+    import phonenumbers
+except Exception:
+    phonenumbers = None
+
+
+bp = Blueprint('public', __name__)
+
+
+@bp.route('/', methods=['GET', 'POST'])
+def index():
+    if request.method == 'POST':
+        vorname = request.form.get('vorname', '').strip()
+        nachname = request.form.get('nachname', '').strip()
+        strasse = request.form.get('strasse', '').strip()
+        hausnummer = request.form.get('hausnummer', '').strip()
+        plz = request.form.get('plz', '').strip()
+        ort = request.form.get('ort', '').strip()
+        land = request.form.get('land', 'Deutschland').strip()
+        telefon_vorwahl = request.form.get('telefon_vorwahl', '').strip()
+        telefon_nummer = request.form.get('telefon_nummer', '').strip()
+        email = request.form.get('email', '').strip()
+
+        errors = {}
+
+        # Email validation: use `email_validator` if present, else fallback regex
+        if email:
+            if validate_email:
+                try:
+                    # disable deliverability checks (MX/DNS) to avoid rejecting
+                    # addresses like max@example.com during testing
+                    valid = validate_email(email, check_deliverability=False)
+                    email = valid.email
+                except EmailNotValidError:
+                    errors['email'] = 'Ungültige E-Mail-Adresse'
+            else:
+                email_re = re.compile(r"[^@]+@[^@]+\.[^@]+")
+                if not email_re.match(email):
+                    errors['email'] = 'Ungültige E-Mail-Adresse'
+
+        # German PLZ: exactly 5 digits
+        if plz:
+            if not plz.isdigit() or len(plz) != 5:
+                errors['plz'] = 'Postleitzahl muss genau 5 Ziffern haben'
+
+        # Phone validation: require both country code and number when provided
+        if telefon_vorwahl or telefon_nummer:
+            if not (telefon_vorwahl and telefon_nummer):
+                errors['telefon'] = 'Vorwahl und Telefonnummer müssen beide angegeben werden'
+            else:
+                if phonenumbers:
+                    raw = telefon_vorwahl.lstrip('+') + telefon_nummer
+                    international = '+' + raw
+                    try:
+                        parsed = phonenumbers.parse(international, None)
+                        if not phonenumbers.is_valid_number(parsed):
+                            errors['telefon'] = 'Ungültige Telefonnummer'
+                    except Exception:
+                        errors['telefon'] = 'Ungültige Telefonnummer'
+                else:
+                    # fallback: basic numeric checks
+                    if not (telefon_vorwahl.lstrip('+').isdigit() and telefon_nummer.isdigit()):
+                        errors['telefon'] = 'Ungültige Telefonnummer'
+                    elif len(telefon_nummer) < 3:
+                        errors['telefon'] = 'Ungültige Telefonnummer'
+
+        if errors:
+            fragen = Frage.query.all()
+            form = request.form.to_dict()
+            return render_template('index.html', fragen=fragen, errors=errors, form=form)
+
+        adresse = Adresse(
+            vorname=vorname,
+            nachname=nachname,
+            strasse=strasse,
+            hausnummer=hausnummer,
+            plz=plz,
+            ort=ort,
+            land=land,
+            telefon_vorwahl=telefon_vorwahl,
+            telefon_nummer=telefon_nummer,
+            email=email,
+        )
+        db.session.add(adresse)
+        db.session.commit()
+
+        fragen = Frage.query.all()
+        for frage in fragen:
+            key = f'frage_{frage.id}'
+            antwort_text = request.form.get(key, '').strip()
+            antwort = Antwort(adresse_id=adresse.id, frage_id=frage.id, text=antwort_text)
+            db.session.add(antwort)
+        db.session.commit()
+
+        try:
+            base_dir = current_app.config.get('BASE_DIR') if current_app.config.get('BASE_DIR') else getattr(current_app, 'BASE_DIR', '.')
+            generate_vcard(adresse, base_dir)
+        except Exception:
+            current_app.logger.exception('Fehler beim Erzeugen der vCard for adresse id=%s', adresse.id if hasattr(adresse, 'id') else 'unknown')
+
+        return redirect(url_for('public.danke', id=adresse.id))
+
+    fragen = Frage.query.all()
+    return render_template('index.html', fragen=fragen)
+
+
+@bp.route('/danke')
+def danke():
+    ad_id = request.args.get('id')
+    adresse = db.session.get(Adresse, int(ad_id)) if ad_id else None
+    return render_template('danke.html', adresse=adresse)
diff --git a/requirements.txt b/requirements.txt
index 161ff2b..1cee769 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,3 +2,5 @@ Flask>=2.0
 Flask-SQLAlchemy>=3.0
 Flask-Migrate>=4.0
 alembic>=1.9
+email-validator>=1.3.1
+phonenumbers>=8.13.0
diff --git a/templates/index.html b/templates/index.html
index d159c3b..5e432a9 100644
--- a/templates/index.html
+++ b/templates/index.html
@@ -20,6 +20,9 @@
         <label>Land <input name="land" value="{{ form.land if form and form.land else 'Deutschland' }}"></label>
         <label>Telefon Vorwahl <input name="telefon_vorwahl" value="{{ form.telefon_vorwahl if form and form.telefon_vorwahl }}"></label>
         <label>Telefon Nummer <input name="telefon_nummer" value="{{ form.telefon_nummer if form and form.telefon_nummer }}"></label>
+        {% if errors and errors.telefon %}
+          <div style="color:red">{{ errors.telefon }}</div>
+        {% endif %}
         <label>E-Mail <input name="email" type="email" value="{{ form.email if form and form.email }}"> {% if errors and errors.email %}<strong style="color:red">{{ errors.email }}</strong>{% endif %}</label>
       </fieldset>
 
diff --git a/tests/test_validation.py b/tests/test_validation.py
new file mode 100644
index 0000000..e36fcd4
--- /dev/null
+++ b/tests/test_validation.py
@@ -0,0 +1,77 @@
+import pytest
+from pathlib import Path
+
+from app import app, db, Frage
+
+
+@pytest.fixture
+def client(tmp_path):
+    db_file = tmp_path / "test.db"
+    app.config['TESTING'] = True
+    app.config['SQLALCHEMY_DATABASE_URI'] = f'sqlite:///{db_file}'
+    app.BASE_DIR = str(tmp_path)
+
+    with app.app_context():
+        db.drop_all()
+        db.create_all()
+        q = Frage(text='Testfrage?')
+        db.session.add(q)
+        db.session.commit()
+        app.config['TEST_QUESTION_ID'] = q.id
+
+    with app.test_client() as test_client:
+        yield test_client
+
+
+def _base_form(question_id):
+    return {
+        'vorname': 'Max',
+        'nachname': 'Mustermann',
+        'strasse': 'Musterstraße',
+        'hausnummer': '1',
+        'plz': '12345',
+        'ort': 'Musterstadt',
+        'land': 'Deutschland',
+        f'frage_{question_id}': 'Antwort'
+    }
+
+
+def test_invalid_email_shows_error(client):
+    qid = app.config.get('TEST_QUESTION_ID')
+    data = _base_form(qid)
+    data.update({'email': 'not-an-email', 'telefon_vorwahl': '', 'telefon_nummer': ''})
+
+    res = client.post('/', data=data)
+    assert res.status_code == 200
+    assert 'Ungültige E-Mail-Adresse' in res.get_data(as_text=True)
+
+
+def test_invalid_phone_shows_error(client):
+    qid = app.config.get('TEST_QUESTION_ID')
+    data = _base_form(qid)
+    # invalid numeric content
+    data.update({'email': 'max@example.com', 'telefon_vorwahl': '49', 'telefon_nummer': 'notnum'})
+
+    res = client.post('/', data=data)
+    assert res.status_code == 200
+    assert 'Ungültige Telefonnummer' in res.get_data(as_text=True)
+
+
+def test_missing_phone_part_shows_error(client):
+    qid = app.config.get('TEST_QUESTION_ID')
+    data = _base_form(qid)
+    data.update({'email': 'max@example.com', 'telefon_vorwahl': '49', 'telefon_nummer': ''})
+
+    res = client.post('/', data=data)
+    assert res.status_code == 200
+    assert 'Vorwahl und Telefonnummer müssen beide angegeben werden' in res.get_data(as_text=True)
+
+
+def test_valid_email_and_phone_redirects(client):
+    qid = app.config.get('TEST_QUESTION_ID')
+    data = _base_form(qid)
+    data.update({'email': 'max@example.com', 'telefon_vorwahl': '49', 'telefon_nummer': '1234567'})
+
+    res = client.post('/', data=data, follow_redirects=False)
+    # successful submission should redirect to /danke
+    assert res.status_code in (302, 303)