1      A mailbox is a "segment" where mail is received and stored.  A mailbox may
 2 also receive messages, if it is specified by the send_messages "command."
 3 Otherwise, deferred messages are placed in a temporary segment which has no
 4 visible name.  Once you read the messages from that segment, the messages
 5 disappear.
 6 
 7      Every mailbox has a name that ends with the suffix '.mbx' (for example:
 8 letters.mbx).  This suffix is added automatically when you create a mailbox,
 9 and whenever you refer to a mailbox when using one of the mail commands, you
10 do not have to include the suffix explicitly in the name.  For example, the
11 "command line":
12 
13 read_mail high_priority
14 
15 will cause read_mail to read from the mailbox named high_priority.mbx.
16 
17      Mailboxes with the '.mbx' suffix may be used for receiving and saving
18 mail.  There are also mailboxes whose name contains the double suffix
19 '.sv.mbx'; these are used exclusively for saving mail that has been received
20 in another mailbox.
21 
22      The first time mail is sent to you, a mailbox is automatically created to
23 receive that mail.  This mailbox is named with your "user name" and the suffix
24 '.mbx' (e.g., JSmith.mbx).  This is the only mailbox created automatically.
25 Any other mailboxes you wish to have for receiving and saving mail must be
26 created with the mbx_create command.  For example, the command line:
27 
28 mbx_create high_priority.sv
29 
30 will create a mailbox named high_priority.sv.mbx.
31 
32      When your mailbox contains more than one piece of mail, each one is
33 assigned a number, and you can refer to them by those numbers.  If you do not
34 give a number when making a request, the request operates on the current
35 piece of mail.  When you enter read_mail, number 1 is automatically current.
36 You can designate another piece to be current by listing it with the list
37 request.  In fact, whenever you request anything be done with a piece of mail,
38 it becomes the current piece, unless, of course, you delete it, in which case
39 the one after it becomes current.