repo.zimbra.com:443; Connection refused

[manusha]

Hi I tried to install Zimbra 8.8.12 , 8.7.11 but didnt worked,
Downloading packages (12):
zimbra-core-components
zimbra-ldap-components
zimbra-mta-components
zimbra-dnscache-components
zimbra-snmp-components
zimbra-store-components
zimbra-jetty-distribution
zimbra-apache-components
zimbra-spell-components
zimbra-memcached
zimbra-proxy-components
zimbra-mta-patch
...Unable to download packages from repository. System is not modified.

so i tried to curl with the url but for some time it says Connection refused, however after 5 or some minutes, i can curl the url then again i can come to this step. Can someone give me help or zimbra need to fix this issue?