How to mask a URL in Directadmin, without changing the URL

[synergynz]

Can you advise if it is possible to mask a URL in directadmin, without changing the URL? Eg, if I want users who enter domain.com/form to be redirected to domain1.com (hosted externally, not on same server) but the URL would still show as domain.com/form Appreciate your help very much. Thank you.