1 files changed, 8 insertions, 0 deletions
diff --git a/app/compose.go b/app/compose.go
index 43ca6610..a54f534b 100644
--- a/app/compose.go
+++ b/app/compose.go
@@ -945,6 +945,14 @@ func (c *Composer) WriteMessage(header *mail.Header, writer io.Writer) error {
 			}
 		}
 
+		if header != nil && !header.Has("MIME-Version") {
+			// sign and encrypt will create multipart/* messages
+			// without setting the MIME-Version header. Set it
+			// manually at the top level to be compliant with RFC
+			// 2045.
+			header.Set("MIME-Version", "1.0")
+		}
+
 		if c.encrypt {
 			rcpts, err := getRecipientsEmail(c)
 			if err != nil {