==================================== 
su courier
                                                                                
cd /home/vmail/$DOMAIN
                                                                                
/usr/lib/courier/sbin/userdb $DOMAIN/$ADDRESS set
home=/home/vmail/$DOMAIN/$USER  uid=502 gid=502
====================================
userdb john@example.com set home=/home/virtual/example.com/john \
             mail=/home/virtual/example.com/john \
             uid=999 gid=999
====================================
/usr/lib/courier/sbin/userdbpw | /usr/lib/courier/sbin/userdb
"$DOMAIN/$USER" set systempw
                                                                                
/usr/lib/courier/sbin/makeuserdb
exit
                                                                                
su vmail
                                                                                
mkdir /home/vmail/$DOMAIN/$USER
                                                                                
cd /home/vmail/$DOMAIN/$USER
                                                                                
maildirmake Maildir
                                                                                
exit
You can then create aliases in the /etc/courier/aliases dir.
$USER@$DOMAIN:   otheruser@otherdomain.com

============================	courier packages
courier-authdaemon - Courier Mail Server authentication daemon
courier-authmysql - MySQL Authentication for Courier Mail Server
courier-base - Courier Mail Server Base System
courier-debug - Debugging Tools for Courier Mail Server
courier-doc - Documentation for the Courier Mail Server
courier-imap - IMAP daemon with PAM and Maildir support
courier-ldap - LDAP support for Courier Mail Server
courier-maildrop - Mail delivery agent with filtering abilities
courier-mlm - Courier Mail Server mailing list manager
courier-mta - Mail Transport Agent of the Courier Mail Server
courier-pcp - Courier PCP server
courier-pop - POP3 daemon with PAM and Maildir support
courier-webadmin - Web-based administration tool for the Courier Mail Server
cvm - Credential Validation Modules
scalable-cyrfonts - scalable Cyrillic fonts
sqwebmail - Webmail Server
xfonts-scalable - scalable fonts for X
xfonts-scalable-nonfree - non-free Type1 and TrueType fonts from XFree86
msttcorefonts - Installer for Microsoft TrueType core fonts
courier-authpostgresql - PostgreSQL Authentication for Courier Mail Server Suite
courier-imap-ssl - IMAP daemon with SSL, PAM and Maildir support
courier-mta-ssl - Courier Mail Transport Agent (SMTP over SSL)
courier-pop-ssl - POP3 daemon with SSL, PAM and Maildir support
courier-ssl - Courier Mail Server SSL Package
==================================== userdbpw
 userdbpw  [   [  -md5]   [  -hmac-md5]   [  -hmac-sha1]  ]
       |userdb name set field
userdbpw -md5 | userdb <userdbfile>/<emailaddress> set systempw
userdbpw -hmac-md5 | userdb users/john set hmac-md5pw
 These commands set the systempw field in  the  record  for
       the  user  john in /etc/courier/userdb/users file, and the
       hmac-md5pw field. Don't forget to run makeuserdb  for  the
       change to take effect.
==================================== 
userdb domain.com/bob@domain.com set home=/home/vmail/domain.com/bob\
	uid=502 gid=502
====================================	
/etc/courier/authdaemonrc
       The  authentication  record is a chunk of data in the fol?
       lowing format:
 
              SERVICE<NEWLINE>AUTHTYPE<NEWLINE>AUTHDATA
 
       Each occurence of <NEWLINE> represents an  ASCII  linefeed
       character  (#10).   "SERVICE"  identifies the service that
       originates the authentication request, such as "imap",  or
       "webmail".  Authentication module may use this identifier,
       or ignore it.
       login  A  typical  userid/password authentication request.
              AUTHDATA contains the following  data:  userid<NEW?
              LINE>password<NEWLINE>.
 
       cram-md5
              Specifies   the  CRAM-MD5  authentication  request.
              AUTHDATA  contains  the   following   data:   chal?
              lenge<NEWLINE>response<NEWLINE>.   The  "challenge"
              and "response" strings are base64-encoded.
 
       cram-sha1
              Specifies  the  CRAM-SHA1  authentication  request,
              instead  of  CRAM-MD5, and uses the same format for
              AUTHDATA.
 
--------------------------------------
       Each line in /etc/courier/userdb takes following form:
 
              addr<TAB>field=value|field=value...
 
       addr specifies a unique virtual address. It is followed by
       a  single tab character, then a list of field=value pairs,
       separated by vertical slash characters. See  makeuserdb(8)
       for field definitions.
 
       A  text  editor can be used to add blank lines or comments
       in /etc/courier/userdb.  Any blank lines or  comments  are
       ignored by the userdb script.
 
       The  names  of  the actual fields, and their contents, are
       defined   entirely   by   applications   that   use    the
       /etc/courier/userdb database, the userdb command just adds
       or removes arbitrary fields.
 
       For example:
 
              userdb default/info set mail=/home/mail/info
 
       This   command   accesses   the    address    "info"    in
       /etc/courier/userdb/default.
 
       If  the  second argument to userdb is "set", the remaining
       arguments are taken as field=value pairs, which are  added
       to  the record for addr. If there is no record for addr, a
       new record will be appended to the file. If  addr  exists,
       any  existing  values of any specified fields are removed.
       If =value is missing, userdb stops  and  prompts  for  it.
       This  is  useful if you're setting a password field, where
       you do not want to specify the  password  on  the  command
       line, which can be seen by the ps(1) command. If userdb is
       being executed by a script, the value can be  provided  on
       standard input.