 DNS"  24),    .  DNS-   
,    Internet-,     MX.

  sendmail

 .      MUA   -
 sendmail,     /var/spool/mqueue  , 
      sendmail.   
      sendmail  
       ,    -
.  sendmail       ,  -
 df ("data file"   ),     . -
        ,  
qf ("queue file"   ),     .

    sendmail    -
,     ,    tf,  
    ,    xf.   
 sendmail    /var/spool/mqueue  , 
  .

 .   '     -
   mbox (.  )     -
 /var/spool/mail.         
,   .         -
,    MUA.       -
 MUA   ,   ,    -
  .

 mbox  maildir.  mbox,  sendmail,   
   .         -
          -
;         -
.   maildir     -
 .     ,   MUA  
      .  , 
maildir        . -
  maildir        
 ,  IMAP.  Qmail (.  "-
 sendmail"    )     maildir.

 

 sendmail      /var/log/maillog.   
       , , 
imapd  ipop3d.     .

634  V.     