Can you enable smtp debug and send the
<install>/zimbra/zdesktop/log/zdesktop.out
Edit this file <install>/zimbra/zdesktop/conf/localconfig.xml
change this code
PHP Code:
<key name="javamail_smtp_debug">
<value>false</value>
</key>
to
PHP Code:
<key name="javamail_smtp_debug">
<value>true</value>
</key>
save the file and restart zdesktop
<install>/zimbra/zdesktop/zdesktop stop
<install>/zimbra/zdesktop/zdesktop start