Symptoms
A Reseller cannot setup Exchange Branding - this menu item is absent in the Service branding section of the Brand properties.
Cause
Hosted Exchange Resource Type is not included into Reseller's subscription.
It could be checked in the pui.log:
****************NEW REQUEST***************
...
{curobj_type=brand}
{action=pcp.TabSelect}
{tab_id=services}
[default task-69] DEBUG c.p.p.c.e.w.exchange.Application - exchange.branding.subtab.variation hasPossibleRC exchange.domainServices= false
This line indicates required Resource Class is not found in scope of Reseller's subscription.
Resolution
Add Hosted Exchange Resource Type into Reseller's subscription.