By default, check "Do Not Send Flowed Text".

Index: pith/conf.c
--- pith/conf.c.orig
+++ pith/conf.c
@@ -2974,7 +2974,7 @@ feature_list(int index)
 	{"use-sender-not-x-sender", "Use Sender Instead of X-X-Sender",
 	 F_USE_SENDER_NOT_X, h_config_use_sender_not_x, PREF_SEND, 0},
 	{"quell-flowed-text", "Do Not Send Flowed Text",
-	 F_QUELL_FLOWED_TEXT, h_config_quell_flowed_text, PREF_SEND, 0},
+	 F_QUELL_FLOWED_TEXT, h_config_quell_flowed_text, PREF_SEND, 1},
 	{"downgrade-multipart-to-text", "Downgrade Multipart to Text",
 	 F_COMPOSE_ALWAYS_DOWNGRADE, h_downgrade_multipart_to_text, PREF_SEND, 0},
 	{"enable-8bit-esmtp-negotiation", "Enable 8bit ESMTP Negotiation",