diff --git a/k9mail/src/test/java/com/fsck/k9/autocrypt/AutocryptGossipHeaderParserTest.kt b/k9mail/src/test/java/com/fsck/k9/autocrypt/AutocryptGossipHeaderParserTest.kt
new file mode 100644
index 000000000..572add784
--- /dev/null
+++ b/k9mail/src/test/java/com/fsck/k9/autocrypt/AutocryptGossipHeaderParserTest.kt
@@ -0,0 +1,96 @@
+package com.fsck.k9.autocrypt
+
+
+import com.fsck.k9.mail.filter.Base64
+import com.fsck.k9.mailstore.MimePartStreamParser
+import org.junit.Assert.*
+import org.junit.Test
+
+
+class AutocryptGossipHeaderParserTest {
+    val GOSSIP_DATA_BOB = Base64.decodeBase64(
+            """mQGNBFoBt74BDAC8AMsjPY17kxodbfmHah38ZQipY0yfuo97WUBs2jeiFYlQdunPANi5VMgbAX+H
+     Mq1XoBRs6qW+WpX8Uj11mu22c57BTUXJRbRr4TnTuuOQmT0egwFDe3x8vHSFmcf9OzG8iKR9ftUE
+     +F2ewrzzmm3XY8hy7QeUgBfClZVA6A3rsX4gGawjDo6ZRBbYwckINgGX/vQk6rGs""".toByteArray())
+
+    val GOSSIP_HEADER_BOB = """addr=bob@autocrypt.example; keydata=
+ mQGNBFoBt74BDAC8AMsjPY17kxodbfmHah38ZQipY0yfuo97WUBs2jeiFYlQdunPANi5VMgbAX+H
+ Mq1XoBRs6qW+WpX8Uj11mu22c57BTUXJRbRr4TnTuuOQmT0egwFDe3x8vHSFmcf9OzG8iKR9ftUE
+ +F2ewrzzmm3XY8hy7QeUgBfClZVA6A3rsX4gGawjDo6ZRBbYwckINgGX/vQk6rGs"""
+
+    val GOSSIP_RAW_HEADER_BOB = "Autocrypt-Gossip: $GOSSIP_HEADER_BOB".replace("\n", "\r\n")
+
+    // Example from Autocrypt 1.0 appendix
+    val GOSSIP_PART = """Autocrypt-Gossip: $GOSSIP_HEADER_BOB
+Autocrypt-Gossip: addr=carol@autocrypt.example; keydata=
+ mQGNBFoBt8oBDADGqfZ6PqW05hUEO1dkKm+ixJXnbVriPz2tRkAqT7lTF4KBGitxo4IPv9RPIjJR
+ UMUo89ddyqQfiwKxdFCMDqFDnVRWlDaM+r8sauNJoIFwtTFuvUpkFeCI5gYvneEIIbf1r3Xx1pf5
+ Iy9qsd5eg/4Vvc2AezUv+A6p2DUNHgFMX2FfDus+EPO0wgeWbNaV601aE7UhyugB
+Content-Type: text/plain
+
+Hi Bob and Carol,
+
+I wanted to introduce the two of you to each other.
+
+I hope you are both doing well!  You can now both "reply all" here,
+and the thread will remain encrypted.
+
+Regards,
+Alice
+""".replace("\n", "\r\n")
+
+    private val autocryptGossipHeaderParser = AutocryptGossipHeaderParser.getInstance()
+
+    @Test
+    fun parseFromPart() {
+        val gossipPart = MimePartStreamParser.parse(null, GOSSIP_PART.byteInputStream())
+        val allAutocryptGossipHeaders = autocryptGossipHeaderParser.getAllAutocryptGossipHeaders(gossipPart)
+
+        assertEquals("text/plain", gossipPart.mimeType)
+        assertEquals(2, allAutocryptGossipHeaders.size)
+        assertEquals("bob@autocrypt.example", allAutocryptGossipHeaders[0].addr)
+        assertEquals("carol@autocrypt.example", allAutocryptGossipHeaders[1].addr)
+        assertArrayEquals(GOSSIP_DATA_BOB, allAutocryptGossipHeaders[0].keyData)
+    }
+
+    @Test
+    fun parseString() {
+        val gossipHeader = autocryptGossipHeaderParser.parseAutocryptGossipHeader(GOSSIP_HEADER_BOB)
+
+        gossipHeader!!
+        assertArrayEquals(GOSSIP_DATA_BOB, gossipHeader.keyData)
+        assertEquals(GOSSIP_RAW_HEADER_BOB, gossipHeader.toRawHeaderString())
+    }
+
+    @Test
+    fun parseHeader_missingKeydata() {
+        val gossipHeader = autocryptGossipHeaderParser.parseAutocryptGossipHeader(
+                "addr=CDEF")
+
+        assertNull(gossipHeader)
+    }
+
+    @Test
+    fun parseHeader_unknownCritical() {
+        val gossipHeader = autocryptGossipHeaderParser.parseAutocryptGossipHeader(
+                "addr=bawb; somecritical=value; keydata=aGk")
+
+        assertNull(gossipHeader)
+    }
+
+    @Test
+    fun parseHeader_unknownNonCritical() {
+        val gossipHeader = autocryptGossipHeaderParser.parseAutocryptGossipHeader(
+                "addr=bawb; _somenoncritical=value; keydata=aGk")
+
+        assertNotNull(gossipHeader)
+    }
+
+    @Test
+    fun parseHeader_brokenBase64() {
+        val gossipHeader = autocryptGossipHeaderParser.parseAutocryptGossipHeader(
+                "addr=bawb; _somenoncritical=value; keydata=X")
+
+        assertNull(gossipHeader)
+    }
+}
\ No newline at end of file
diff --git a/k9mail/src/test/java/com/fsck/k9/message/PgpMessageBuilderTest.java b/k9mail/src/test/java/com/fsck/k9/message/PgpMessageBuilderTest.java
index 025d3a472..a8aa3467a 100644
--- a/k9mail/src/test/java/com/fsck/k9/message/PgpMessageBuilderTest.java
+++ b/k9mail/src/test/java/com/fsck/k9/message/PgpMessageBuilderTest.java
@@ -330,6 +330,66 @@ public class PgpMessageBuilderTest {
         verifyNoMoreInteractions(mockCallback);
     }
 
+    @Test
+    public void buildEncrypt__checkGossip() throws MessagingException {
+        ComposeCryptoStatus cryptoStatus = cryptoStatusBuilder
+                .setCryptoMode(CryptoMode.CHOICE_ENABLED)
+                .setRecipients(Arrays.asList(
+                        new Recipient("alice", "alice@example.org", "alice", -1, "key"),
+                        new Recipient("bob", "bob@example.org", "bob", -1, "key2")))
+                .build();
+        pgpMessageBuilder.setCryptoStatus(cryptoStatus);
+
+        Intent returnIntent = new Intent();
+        returnIntent.putExtra(OpenPgpApi.RESULT_CODE, OpenPgpApi.RESULT_CODE_SUCCESS);
+        when(openPgpApi.executeApi(any(Intent.class), any(OpenPgpDataSource.class), any(OutputStream.class))).thenReturn(returnIntent);
+        pgpMessageBuilder.buildAsync(mock(Callback.class));
+
+        verify(autocryptOpenPgpApiInteractor).getKeyMaterialForUserId(same(openPgpApi), eq("alice@example.org"));
+        verify(autocryptOpenPgpApiInteractor).getKeyMaterialForUserId(same(openPgpApi), eq("bob@example.org"));
+    }
+
+    @Test
+    public void buildEncrypt__checkGossip__filterBcc() throws MessagingException {
+        ComposeCryptoStatus cryptoStatus = cryptoStatusBuilder
+                .setCryptoMode(CryptoMode.CHOICE_ENABLED)
+                .setRecipients(Arrays.asList(
+                        new Recipient("alice", "alice@example.org", "alice", -1, "key"),
+                        new Recipient("bob", "bob@example.org", "bob", -1, "key2"),
+                        new Recipient("carol", "carol@example.org", "carol", -1, "key3")))
+                .build();
+        pgpMessageBuilder.setCryptoStatus(cryptoStatus);
+        pgpMessageBuilder.setBcc(Collections.singletonList(new Address("carol@example.org")));
+
+        Intent returnIntent = new Intent();
+        returnIntent.putExtra(OpenPgpApi.RESULT_CODE, OpenPgpApi.RESULT_CODE_SUCCESS);
+        when(openPgpApi.executeApi(any(Intent.class), any(OpenPgpDataSource.class), any(OutputStream.class))).thenReturn(returnIntent);
+        pgpMessageBuilder.buildAsync(mock(Callback.class));
+
+        verify(autocryptOpenPgpApiInteractor).getKeyMaterialForUserId(same(openPgpApi), eq("alice@example.org"));
+        verify(autocryptOpenPgpApiInteractor).getKeyMaterialForUserId(same(openPgpApi), eq("bob@example.org"));
+    }
+
+    @Test
+    public void buildEncrypt__checkGossip__filterBccSingleRecipient() throws MessagingException {
+        ComposeCryptoStatus cryptoStatus = cryptoStatusBuilder
+                .setCryptoMode(CryptoMode.CHOICE_ENABLED)
+                .setRecipients(Arrays.asList(
+                        new Recipient("alice", "alice@example.org", "alice", -1, "key"),
+                        new Recipient("carol", "carol@example.org", "carol", -1, "key3")))
+                .build();
+        pgpMessageBuilder.setCryptoStatus(cryptoStatus);
+        pgpMessageBuilder.setBcc(Collections.singletonList(new Address("carol@example.org")));
+
+        Intent returnIntent = new Intent();
+        returnIntent.putExtra(OpenPgpApi.RESULT_CODE, OpenPgpApi.RESULT_CODE_SUCCESS);
+        when(openPgpApi.executeApi(any(Intent.class), any(OpenPgpDataSource.class), any(OutputStream.class))).thenReturn(returnIntent);
+        pgpMessageBuilder.buildAsync(mock(Callback.class));
+
+        verify(autocryptOpenPgpApiInteractor).getKeyMaterialForKeyId(any(OpenPgpApi.class), any(Long.class), any(String.class));
+        verifyNoMoreInteractions(autocryptOpenPgpApiInteractor);
+    }
+
     @Test
     public void buildEncrypt__shouldSucceed() throws MessagingException {
         ComposeCryptoStatus cryptoStatus = cryptoStatusBuilder