First create a directory
Code:
/opt/zimbra/jetty/webapps/zimbra/skins/_base/myskin
then copy your customized files
Code:
AppBanner.png
LoginBanner.png
to this directory. Now you can point to your custom Logos. In the Admin GUI go to General Setting -> Styles. The path to your custom Logos is
Code:
/zimbra/skins/_base/myskin/AppBanner.png
/zimbra/skins/_base/myskin/LoginBanner.png
Pointing to external images files with a full http:// URL will cause security warnings from the Browser.
Please note that this will be overwritten by the next update. So have to copy the files again.