diff --git a/app/src/main/java/eu/faircode/email/FragmentGmail.java b/app/src/main/java/eu/faircode/email/FragmentGmail.java
index c8f55e0921..ce23e4cbb9 100644
--- a/app/src/main/java/eu/faircode/email/FragmentGmail.java
+++ b/app/src/main/java/eu/faircode/email/FragmentGmail.java
@@ -300,7 +300,7 @@ public class FragmentGmail extends FragmentBase {
                 String password = args.getString("password");
 
                 // Safety checks
-                if (!Patterns.EMAIL_ADDRESS.matcher(user).matches())
+                if (!Helper.EMAIL_ADDRESS.matcher(user).matches())
                     throw new IllegalArgumentException(context.getString(R.string.title_email_invalid, user));
                 if (TextUtils.isEmpty(password))
                     throw new IllegalArgumentException(context.getString(R.string.title_no_password));
diff --git a/app/src/main/java/eu/faircode/email/FragmentIdentity.java b/app/src/main/java/eu/faircode/email/FragmentIdentity.java
index 10000813b0..890737b257 100644
--- a/app/src/main/java/eu/faircode/email/FragmentIdentity.java
+++ b/app/src/main/java/eu/faircode/email/FragmentIdentity.java
@@ -657,7 +657,7 @@ public class FragmentIdentity extends FragmentBase {
                     throw new IllegalArgumentException(context.getString(R.string.title_no_name));
                 if (TextUtils.isEmpty(email) && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_email));
-                if (!Patterns.EMAIL_ADDRESS.matcher(email).matches() && !should)
+                if (!Helper.EMAIL_ADDRESS.matcher(email).matches() && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_email_invalid, email));
                 if (TextUtils.isEmpty(host) && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_host));
diff --git a/app/src/main/java/eu/faircode/email/FragmentOAuth.java b/app/src/main/java/eu/faircode/email/FragmentOAuth.java
index 9b37889b6a..50ff412102 100644
--- a/app/src/main/java/eu/faircode/email/FragmentOAuth.java
+++ b/app/src/main/java/eu/faircode/email/FragmentOAuth.java
@@ -217,7 +217,7 @@ public class FragmentOAuth extends FragmentBase {
 
                 if (TextUtils.isEmpty(email))
                     throw new IllegalArgumentException(getString(R.string.title_no_email));
-                if (!Patterns.EMAIL_ADDRESS.matcher(email).matches())
+                if (!Helper.EMAIL_ADDRESS.matcher(email).matches())
                     throw new IllegalArgumentException(getString(R.string.title_email_invalid, email));
             }
 
diff --git a/app/src/main/java/eu/faircode/email/FragmentQuickSetup.java b/app/src/main/java/eu/faircode/email/FragmentQuickSetup.java
index ed067a1c5a..508057ab3f 100644
--- a/app/src/main/java/eu/faircode/email/FragmentQuickSetup.java
+++ b/app/src/main/java/eu/faircode/email/FragmentQuickSetup.java
@@ -256,7 +256,7 @@ public class FragmentQuickSetup extends FragmentBase {
                     throw new IllegalArgumentException(context.getString(R.string.title_no_name));
                 if (TextUtils.isEmpty(email))
                     throw new IllegalArgumentException(context.getString(R.string.title_no_email));
-                if (!Patterns.EMAIL_ADDRESS.matcher(email).matches())
+                if (!Helper.EMAIL_ADDRESS.matcher(email).matches())
                     throw new IllegalArgumentException(context.getString(R.string.title_email_invalid, email));
                 if (TextUtils.isEmpty(password))
                     throw new IllegalArgumentException(context.getString(R.string.title_no_password));
diff --git a/app/src/main/java/eu/faircode/email/Helper.java b/app/src/main/java/eu/faircode/email/Helper.java
index c3583c44f0..4d874a1411 100644
--- a/app/src/main/java/eu/faircode/email/Helper.java
+++ b/app/src/main/java/eu/faircode/email/Helper.java
@@ -127,6 +127,7 @@ import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.regex.Pattern;
 
 import static android.os.Process.THREAD_PRIORITY_BACKGROUND;
 import static androidx.browser.customtabs.CustomTabsService.ACTION_CUSTOM_TABS_CONNECTION;
@@ -151,6 +152,17 @@ public class Helper {
     static final String CROWDIN_URI = "https://crowdin.com/project/open-source-email";
     static final String GRAVATAR_PRIVACY_URI = "https://meta.stackexchange.com/questions/44717/is-gravatar-a-privacy-risk";
 
+    static final Pattern EMAIL_ADDRESS
+            = Pattern.compile(
+            "[\\S]{1,256}" +
+                    "\\@" +
+                    "[a-zA-Z0-9][a-zA-Z0-9\\-]{0,64}" +
+                    "(" +
+                    "\\." +
+                    "[a-zA-Z0-9][a-zA-Z0-9\\-]{0,25}" +
+                    ")+"
+    );
+
     static ExecutorService getBackgroundExecutor(int threads, final String name) {
         ThreadFactory factory = new ThreadFactory() {
             private final AtomicInteger threadId = new AtomicInteger();