how to create user name with dot with cyrus 2.0.17

[sam]

Hi,

I m using version 2.0.17.
Trying to create a user name with dot, but it seems doesn't allow me to 
do so.
The following is the confi of imapd.conf:

admins:  cyrus
allowanonymouslogin:  no
allowplainwithouttls: yes
allowplaintext: yes
altnamespace: yes
autocreatequota:  10000
configdirectory:  /var/db/imap
drachost:  localhost
dracinterval:  0
duplicatesuppression: yes
lmtp_overquota_perm_failure: no
lmtpsocket: /var/spool/imap/public/lmtp
normalizeuid: yes
partition-default:  /var/spool/imap
poptimeout:  10
quotawarn:  90
reject8bit:  no
sasl_mech_list: plain login
sasl_pwcheck_method: sasldb
#sasl_pwcheck_method: saslauthd
#sasl_pwcheck_method: auxprop
#sasl_pwcheck_method: pwcheck
sievedir: /var/imap/sieve
timeout:  30
tls_ca_file: /root/at-keys/ca.crt
tls_ca_path: /root/at-keys
tls_cert_file: /root/at-keys/gateway.crt
tls_key_file: /root/at-keys/gateway.key
unixhierarchysep: yes

virtdomains: yes
defaultdomain: authtec.com
lmtp_downcase_rcpt: true
loginrealms: mydot.com mydot.net

hashimapspool: false
fulldirhash: true

Does anyone know how can I create a user name with dot in 2.0.17?

Thanks
sam

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