--- a/src/lib-mail/message-address.c	Fri Jul 22 13:09:40 2011 +0300
+++ b/src/lib-mail/message-address.c	Fri Jul 22 13:10:09 2011 +0300
@@ -400,3 +400,20 @@
 		addr = addr->next;
 	}
 }
+
+static const char *address_headers[] = {
+	"From", "Sender", "Reply-To",
+	"To", "Cc", "Bcc",
+	"Resent-From", "Resent-Sender", "Resent-To", "Resent-Cc", "Resent-Bcc"
+};
+
+bool message_header_is_address(const char *hdr_name)
+{
+	unsigned int i;
+
+	for (i = 0; i < N_ELEMENTS(address_headers); i++) {
+		if (strcasecmp(hdr_name, address_headers[i]) == 0)
+			return TRUE;
+	}
+	return FALSE;
+}

--- a/src/lib-mail/message-address.h	Fri Jul 22 13:09:40 2011 +0300
+++ b/src/lib-mail/message-address.h	Fri Jul 22 13:10:09 2011 +0300
@@ -30,4 +30,7 @@
 
 void message_address_write(string_t *str, const struct message_address *addr);
 
+/* Returns TRUE if header is known to be an address */
+bool message_header_is_address(const char *hdr_name);
+
 #endif