webmail with redirecting domain

[gate2vn]

So, the customer has a domain domain1.com, hosting on server A. The domain is redirecting 301 to domain2.com, running on server B.

When I was running nginx apache, the domain1.com/webmail was working fine. It's just directed to the real URL domain1.com/roundcube
When I converted to OLS, the domain1.com/webmail is no longer working. Any domain1.com/alias-here is redirecting to domain2.com.

I checked the file /usr/local/lsws/conf/httpd-alias.conf, it seems to be fine.

context /webmail/ {
                location                /var/www/html/roundcube/
                include /usr/local/lsws/conf/httpd-webapps-php.conf
        }

In /usr/local/directadmin/data/users/customer-username/openlitespeed.conf, I see rewrite rule but also include alias.

rewrite  {
    enable                  1
    autoLoadHtaccess        1
    RewriteRule ^//?(.*)$ http://domain2.com/$1 [L,R=301]
  }

  # include aliases
  include /usr/local/lsws/conf/httpd-alias.conf

Did I miss anything? Or do I need to have extra rewrite rules for keeping webmail in the current server, not redirecting?