diff --git a/src/engine/rfc822/rfc822-mailbox-address.vala b/src/engine/rfc822/rfc822-mailbox-address.vala
index eda28fe1..5ead3307 100644
--- a/src/engine/rfc822/rfc822-mailbox-address.vala
+++ b/src/engine/rfc822/rfc822-mailbox-address.vala
@@ -445,12 +445,14 @@ public class Geary.RFC822.MailboxAddress :
      * brackets.
      */
     public string to_rfc822_address() {
-        // XXX GMime.utils_header_encode_text won't quote if spaces or
-        // quotes present, and GMime.utils_quote_string will
-        // erroneously quote if a '.'  is present (which at least
-        // Yahoo doesn't like in SMTP return paths), so need to quote
+        // GMime.utils_header_encode_text won't quote if spaces or
+        // quotes present, GMime.utils_quote_string will erroneously
+        // quote if a '.'  is present (which at least Yahoo doesn't
+        // like in SMTP return paths), and
+        // GMime.utils_header_encode_text will use MIME encoding,
+        // which is disallowed in mailboxes by RFC 2074 §5. So quote
         // manually.
-        string local_part = GMime.utils_header_encode_text(this.mailbox);
+        string local_part = this.mailbox;
         if (local_part_needs_quoting(local_part)) {
             local_part = quote_string(local_part);
         }
diff --git a/test/engine/rfc822-mailbox-address-test.vala b/test/engine/rfc822-mailbox-address-test.vala
index d65a5869..9aa2b9e7 100644
--- a/test/engine/rfc822-mailbox-address-test.vala
+++ b/test/engine/rfc822-mailbox-address-test.vala
@@ -238,6 +238,15 @@ class Geary.RFC822.MailboxAddressTest : TestCase {
             new MailboxAddress(null, "test@test@example.com").to_rfc822_address()
         );
 
+        // RFC 2047 reserved words in the local-part must be used
+        // as-is, and in particular not encoded per that RFC. See RFC
+        // 2047 §5 and GNOME/geary#336
+        string RFC_2074 = "libc-alpha-sc.1553427554.ndgdflaalknmibgfkpak-hi-angel=yandex.ru@sourceware.org";
+        assert_string(
+            RFC_2074,
+            new MailboxAddress(null, RFC_2074).to_rfc822_address()
+        );
+
         // Likewise, Unicode chars should be passed through. Note that
         // these can only be sent if a UTF8 connection is negotiated
         // with the SMTP server