[webizen]

thanks for the confirmation.

here is the wrap-up:

vhost accepts https request:

https://portal.domain.com/webmail

.htaccess rewrite rule in question should be proxy to http (not https) as follows:

RewriteRule ^(.*)$ http://webmail/$1 [P]

webmail is the 'web server' type ext app pointing to 127.0.0.1:2080