-\fBf <regexp>\fR (from) selects mails whose leading line From, or
-fields From:, or Reply-To: matches the regexp.
+\fBf <regexp>\fR (from)
+selects mails whose leading line 'From', or fields From:, Sender:,
+Reply-To:, or Return-Path: matches the regexp.
+.TP
+\fBt <regexp>\fR (to)
+selects mails whose field To:, Cc:, or Bcc: matches the regexp.
+.TP
+\fBp <regexp>\fR (participant)
+selects mails that would be selected by \fBf\fR or \fBt\fR.
+.TP
+\fBs <regexp>\fR (subject)
+selects mails whose field Subject: matches the regexp.