Limit messages size to 10 MB

FAQ.md

@@ -2546,6 +2546,9 @@ FairEmail will workaround this is in most cases, so this message can mostly be c
 The error *...SendFailedException...* means that there was a problem while sending a message.
 The error will almost always include a reason. Common reasons are that the message was too big or that one or more recipient addresses were invalid.
 
+The warning *Message too large to fit into the available memory* means that the message was larger than 10 MiB.
+Even if your device has plenty of storage space Android provides limited working memory to apps, which limits the size of messages that can be handled.
+
 Please see [here](#user-content-faq22) for other error messages in the outbox.
 
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app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -93,6 +93,7 @@ public class MessageHelper {
     private MimeMessage imessage;
 
     static final int SMALL_MESSAGE_SIZE = 64 * 1024; // bytes
+    static final int MAX_MESSAGE_SIZE = 10 * 1024 * 1024; // bytes
     static final int DEFAULT_ATTACHMENT_DOWNLOAD_SIZE = 256 * 1024; // bytes
     static final long ATTACHMENT_PROGRESS_UPDATE = 1500L; // milliseconds
 
@@ -1250,6 +1251,10 @@ public class MessageHelper {
 
             String result;
             Part part = (html == null ? plain : html);
+            if (part.getSize() > MAX_MESSAGE_SIZE) {
+                warnings.add(context.getString(R.string.title_insufficient_memory));
+                return null;
+            }
 
             try {
                 Object content = part.getContent();

app/src/main/res/values/strings.xml

@@ -701,6 +701,7 @@
     <string name="title_no_search">Search on server is not available for this account</string>
     <string name="title_too_large">Message too large to completely reformat</string>
     <string name="title_truncated">Message too large to display completely</string>
+    <string name="title_insufficient_memory">Message too large to fit into the available memory</string>
     <string name="title_show_full">Show full message</string>
     <string name="title_unused_inline">Unused inline images will be removed on send</string>
     <string name="title_accross_remark">Messages moved across accounts will be downloaded again resulting in extra data usage</string>