File: //usr/share/webmin/virtual-server/help/config_from_reseller.html
<header>From: address to email sent to domain owners</header>
If a virtual server is owned by a reseller, you may want email send by
Virtualmin (such as bandwidth quota warnings or new script notifications) to
come from the reseller's email address, rather than the master sysadmin. To
enable this, select <b>Reseller's address (if any)</b> - otherwise, leave
<b>Address set above</b> selected. <p>
If a virtual server does not have a reseller or the reseller doesn't have
an address, the <b>Reseller's address</b> mode will fall back to using the
global From: address instead. <p>
<footer>