--- a/src/header.h
+++ b/src/header.h
@@ -168,3 +168,5 @@
 X(readreceiptto,	"Read-Receipt-To:")	  /* miscellaneous extension */
 X(fakesender,		"Fake-Sender:")
 X(envelopeto,		"Envelope-To:")			   /* exim extension */
+X(useragent,		"User-Agent:")
+X(nntppostingdate,	"NNTP-Posting-Date:")
