diff --git a/app/src/main/java/eu/faircode/email/Core.java b/app/src/main/java/eu/faircode/email/Core.java
index 54d977ebf6..30a51765bd 100644
--- a/app/src/main/java/eu/faircode/email/Core.java
+++ b/app/src/main/java/eu/faircode/email/Core.java
@@ -331,7 +331,7 @@ class Core {
                                     break;
 
                                 case EntityOperation.ADD:
-                                    onAdd(context, jargs, folder, message, (IMAPStore) istore, (IMAPFolder) ifolder, state);
+                                    onAdd(context, jargs, account, folder, message, (IMAPStore) istore, (IMAPFolder) ifolder, state);
                                     break;
 
                                 case EntityOperation.MOVE:
@@ -773,7 +773,7 @@ class Core {
         }
     }
 
-    private static void onAdd(Context context, JSONArray jargs, EntityFolder folder, EntityMessage message, IMAPStore istore, IMAPFolder ifolder, State state) throws MessagingException, IOException {
+    private static void onAdd(Context context, JSONArray jargs, EntityAccount account, EntityFolder folder, EntityMessage message, IMAPStore istore, IMAPFolder ifolder, State state) throws MessagingException, IOException {
         // Add message
         DB db = DB.getInstance(context);
 
@@ -788,6 +788,19 @@ class Core {
         if (target != folder.id)
             throw new IllegalArgumentException("Invalid folder");
 
+        // Check size
+        if (account.max_size != null && BuildConfig.DEBUG) {
+            long size = MessageHelper.HEADERS_SIZE;
+            if (message.content)
+                size += message.getFile(context).length();
+            List<EntityAttachment> attachments = db.attachment().getAttachments(message.id);
+            for (EntityAttachment attachment : attachments)
+                if (attachment.available)
+                    size += attachment.size;
+            if (size > account.max_size)
+                throw new IllegalArgumentException("Message too large");
+        }
+
         // External draft might have a uid only
         if (TextUtils.isEmpty(message.msgid)) {
             message.msgid = EntityMessage.generateMessageId();
diff --git a/app/src/main/java/eu/faircode/email/EmailService.java b/app/src/main/java/eu/faircode/email/EmailService.java
index 9a10bfe12a..5a4ab7d427 100644
--- a/app/src/main/java/eu/faircode/email/EmailService.java
+++ b/app/src/main/java/eu/faircode/email/EmailService.java
@@ -635,6 +635,8 @@ public class EmailService implements AutoCloseable {
     }
 
     Long getMaxSize() throws MessagingException {
+        // https://support.google.com/mail/answer/6584#limit
+
         String size;
         if (iservice instanceof SMTPTransport) {
             // https://tools.ietf.org/html/rfc1870
diff --git a/app/src/main/java/eu/faircode/email/FragmentCompose.java b/app/src/main/java/eu/faircode/email/FragmentCompose.java
index 80bcbfada0..716e8b86e5 100644
--- a/app/src/main/java/eu/faircode/email/FragmentCompose.java
+++ b/app/src/main/java/eu/faircode/email/FragmentCompose.java
@@ -264,7 +264,6 @@ public class FragmentCompose extends FragmentBase {
     private static final int REDUCED_IMAGE_QUALITY = 90; // percent
 
     private static final int RECIPIENTS_WARNING = 10;
-    private static final int HEADERS_SIZE = 32 * 1024; // bytes
 
     private static final int REQUEST_CONTACT_TO = 1;
     private static final int REQUEST_CONTACT_CC = 2;
@@ -4283,7 +4282,7 @@ public class FragmentCompose extends FragmentBase {
 
                             // Check size
                             if (identity != null && identity.max_size != null) {
-                                long size = HEADERS_SIZE + body.length();
+                                long size = MessageHelper.HEADERS_SIZE + body.length();
                                 for (EntityAttachment attachment : attachments)
                                     if (attachment.available)
                                         size += attachment.size;
diff --git a/app/src/main/java/eu/faircode/email/MessageHelper.java b/app/src/main/java/eu/faircode/email/MessageHelper.java
index 68ddfa4130..c56ac68491 100644
--- a/app/src/main/java/eu/faircode/email/MessageHelper.java
+++ b/app/src/main/java/eu/faircode/email/MessageHelper.java
@@ -109,6 +109,7 @@ public class MessageHelper {
 
     static final int SMALL_MESSAGE_SIZE = 64 * 1024; // bytes
     static final int DEFAULT_ATTACHMENT_DOWNLOAD_SIZE = 256 * 1024; // bytes
+    static final int HEADERS_SIZE = 32 * 1024; // bytes
     static final String HEADER_CORRELATION_ID = "X-Correlation-ID";
 
     private static final int MAX_MESSAGE_SIZE = 10 * 1024 * 1024; // bytes