-displays a message, that message will be removed from
-any sequences named by the \*(lqUnseen\-Sequence\*(rq entry in the
-profile.
+displays a message, that message will be removed from any sequences
+named by the \*(lqUnseen\-Sequence\*(rq entry in the profile.
+.SS Sequence File Format
+The sequence file format is based on the RFC 5322 message format. Each line
+of the sequence file corresponds to one sequence. The line starts with the
+sequence name followed by a `:', then followed by a space-separated list of
+message numbers that correspond to messages that are part of the named sequence.
+A contiguous range of messages can be represented as \*(lqlownum\-highnum\*(rq.
+.PP
+.B Sample sequence file
+.PP
+.RS 5
+.nf
+work: 3 6 8 22-33 46
+unseen: 47 49-51 54
+cur: 46
+.fi
+.RE
+.PP
+.B Nmh
+commands that modify the sequence file will silently remove sequences for
+nonexistent messages when the sequence file is updated. The exception to
+this is the \*(lqcur\*(rq sequence, which is allowed to point to a
+nonexistent message.