https://documentation.cpanel.net/display/DD/WHM+API+1+Functions+-+unset_all_service_proxy_backends is probably the best solution but it removes all proxies. How do we check if other proxies are configured before we delete all of them?
I success, thanks you !!@albatroz give this a try:
cut -d":" -f1 /etc/trueuserowners | while read user;do whmapi1 unset_all_service_proxy_backends username=$user;done
If only one account was transferred then:
whmapi1 unset_all_service_proxy_backends username=cpanelusername