How to correct Dovecot user login to use full domain email in this format "[email protected]" [duplicate]

I have configured dovecot and postfix...Email server works fine.. (Webmail and outlook both works..) I have created users using unix command ..

usreadd -s /sbin/nologin myuser

But i have a concern, if i want to login to webmail or outlook I have to use myuser instead of [email protected].

For the time being im using, only user name as below..

If i use [email protected] it says its invalid user both webmail and outlook..

I tried googling .. no luck.. yet.. kindly some one please shed a light..

10-master.conf is

#default_process_limit = 100
#default_client_limit = 1000

# Default VSZ (virtual memory size) limit for service processes. This is mainly
# intended to catch and kill processes that leak memory before they eat up
# everything.
#default_vsz_limit = 256M

# Login user is internally used by login processes. This is the most untrusted
# user in Dovecot system. It shouldn't have access to anything at all.
#default_login_user = dovenull

# Internal user is used by unprivileged processes. It should be separate from
# login user, so that login processes can't disturb other processes.
#default_internal_user = dovecot

service imap-login {
  inet_listener imap {
    #port = 143
  }
  inet_listener imaps {
    #port = 993
    #ssl = yes
  }

  # Number of connections to handle before starting a new process. Typically
  # the only useful values are 0 (unlimited) or 1. 1 is more secure, but 0
  # is faster. <doc/wiki/LoginProcess.txt>
  #service_count = 1

  # Number of processes to always keep waiting for more connections.
  #process_min_avail = 0

  # If you set service_count=0, you probably need to grow this.
  #vsz_limit = 64M
}

service pop3-login {
  inet_listener pop3 {
    #port = 110
  }
  inet_listener pop3s {
    #port = 995
    #ssl = yes
  }
}

service lmtp {
  unix_listener lmtp {
   # mode = 0666
  }

  # Create inet listener only if you can't use the above UNIX socket
  #inet_listener lmtp {
    # Avoid making LMTP visible for the entire internet
    #address =
    #port = 
  #}
}

service imap {
  # Most of the memory goes to mmap()ing files. You may need to increase this
  # limit if you have huge mailboxes.
  #vsz_limit = 256M

  # Max. number of IMAP processes (connections)
  #process_limit = 1024
}

service pop3 {
  # Max. number of POP3 processes (connections)
  #process_limit = 1024
}

service auth {
  # auth_socket_path points to this userdb socket by default. It's typically
  # used by dovecot-lda, doveadm, possibly imap process, etc. Its default
  # permissions make it readable only by root, but you may need to relax these
  # permissions. Users that have access to this socket are able to get a list
  # of all usernames and get results of everyone's userdb lookups.
 # unix_listener auth-userdb {
 #   mode = 0600
 #   user = postfix
 #   group = postfix
 # }

   #Postfix smtp-auth
  unix_listener /var/spool/postfix/private/auth {
  mode = 0666
  user = postfix
  group = postfix  
}

  # Auth process is run as this user.
  #user = $default_internal_user
}

service auth-worker {
  # Auth worker process is run as root by default, so that it can access
  # /etc/shadow. If this isn't necessary, the user should be changed to
  # $default_internal_user.
  #user = root
}

service dict {
  # If dict proxy is used, mail processes should have access to its socket.
  # For example: mode=0660, group=vmail and global mail_access_groups=vmail
  unix_listener dict {
    #mode = 0600
    #user = 
    #group = 
  }
}

Results for dovecot -n

# 2.0.9: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-042stab093.4 x86_64 CentOS release 6.6 (Final)
auth_mechanisms = login plain
disable_plaintext_auth = no
mail_location = maildir:~/Maildir
mbox_write_locks = fcntl
passdb {
  driver = pam
}
service auth {
  unix_listener /var/spool/postfix/private/auth {
    group = postfix
    mode = 0666
    user = postfix
  }
}
ssl_cert = </etc/pki/tls/certs/mycert.crt
ssl_key = </etc/pki/tls/private/mycert.key
userdb {
  driver = passwd
}