--- a/src/lib-mail/message-header-hash.c	Thu Jun 22 11:43:05 2017 +0300
+++ b/src/lib-mail/message-header-hash.c	Fri Jun 23 09:14:40 2017 +0300
@@ -30,14 +30,20 @@
 	   remove any repeated '?', which hopefully will satisfy everybody.
 	*/
 	for (i = start = 0; i < size; i++) {
-		if ((data[i] < 0x20 || data[i] >= 0x7f || data[i] == '?') &&
-		    (data[i] != '\t' && data[i] != '\n')) {
-			/* remove repeated '?' */
-			if (start < i || (i == 0 && !ctx->prev_was_questionmark)) {
-				method->loop(context, data + start, i-start);
-				method->loop(context, "?", 1);
+		switch (data[i]) {
+		case '\t':
+		case '\n':
+			break;
+		default:
+			if (data[i] < 0x20 || data[i] >= 0x7f || data[i] == '?') {
+				/* remove repeated '?' */
+				if (start < i || (i == 0 && !ctx->prev_was_questionmark)) {
+					method->loop(context, data + start, i-start);
+					method->loop(context, "?", 1);
+				}
+				start = i+1;
 			}
-			start = i+1;
+			break;
 		}
 	}
 	ctx->prev_was_questionmark = start == i;