diff --git a/src/com/fsck/k9/mail/filter/Base64.java b/src/com/fsck/k9/mail/filter/Base64.java
index 934c3b222..8d5ecf9e7 100644
--- a/src/com/fsck/k9/mail/filter/Base64.java
+++ b/src/com/fsck/k9/mail/filter/Base64.java
@@ -33,7 +33,7 @@ import java.nio.charset.Charset;
  * @since 1.0-dev
  * @version $Id$
  */
-public class Base64 {
+class Base64 {
     /**
      * Chunk size per RFC 2045 section 6.8.
      *
diff --git a/src/com/fsck/k9/mail/internet/BinaryTempFileMessageBody.java b/src/com/fsck/k9/mail/internet/BinaryTempFileMessageBody.java
index c1503b342..62b4d71fc 100644
--- a/src/com/fsck/k9/mail/internet/BinaryTempFileMessageBody.java
+++ b/src/com/fsck/k9/mail/internet/BinaryTempFileMessageBody.java
@@ -16,7 +16,7 @@ import com.fsck.k9.mail.MessagingException;
  * {@link LocalAttachmentMessageBody} relates to a {@link LocalAttachmentBody}.
  *
  */
-public class BinaryTempFileMessageBody extends BinaryTempFileBody implements CompositeBody {
+class BinaryTempFileMessageBody extends BinaryTempFileBody implements CompositeBody {
 
     @Override
     public void setEncoding(String encoding) throws MessagingException {
diff --git a/src/com/fsck/k9/mail/internet/DecoderUtil.java b/src/com/fsck/k9/mail/internet/DecoderUtil.java
index 80d5b573e..3ac74947d 100644
--- a/src/com/fsck/k9/mail/internet/DecoderUtil.java
+++ b/src/com/fsck/k9/mail/internet/DecoderUtil.java
@@ -21,7 +21,7 @@ import org.apache.james.mime4j.util.CharsetUtil;
  * decode emoji characters in the Subject headers.  The method to decode emoji depends on the MimeMessage class because
  * it has to be determined with the sender address, the mailer and so on.
  */
-public class DecoderUtil {
+class DecoderUtil {
     /**
      * Decodes an encoded word encoded with the 'B' encoding (described in
      * RFC 2047) found in a header field body.
diff --git a/src/com/fsck/k9/mail/internet/EncoderUtil.java b/src/com/fsck/k9/mail/internet/EncoderUtil.java
index c5e8bf667..5e7672715 100644
--- a/src/com/fsck/k9/mail/internet/EncoderUtil.java
+++ b/src/com/fsck/k9/mail/internet/EncoderUtil.java
@@ -16,7 +16,7 @@ import org.apache.james.mime4j.util.CharsetUtil;
  * encode emoji characters in the Subject headers.  The method to decode emoji depends on the MimeMessage class because
  * it has to be determined with the sender address.
  */
-public class EncoderUtil {
+class EncoderUtil {
     private static final BitSet Q_RESTRICTED_CHARS = initChars("=_?\"#$%&'(),.:;<>@[\\]^`{|}~");
 
     private static final String ENC_WORD_PREFIX = "=?";