preserve host in ErrorDocument

[eric tse <hfetse@xxxxxxxxx>]

Currently we have

<VirtualHost 142.xx.xxx.xx:443>

ServerName website.domain.com


ErrorDocument 503 http://errorserver.domain.com:44441

SSLEngine On
.......

.........

SSLProxyEngine on
ProxyPreserveHost on
ProxyPass / https://backend.domain.com:8637/
ProxyPassReverse / https://backend.domain.com:8637/

</VirtualHost>

When we have 503. It redirects to  http://errorserver.domain.com:44441

We want to make some changes so that it preservehost to website.domain.com while redirecting

to errorserver.domain.com

My colleagues of thinking.. 

- moving the error pages to /htdocs/error on website.domain.com

- move the  ErrorDocument after  ProxyPreserveHost

Can you please help?

Thanks and regards,
Eric