Agency client portals get built enthusiastically and abandoned quietly, usually around month three, when maintaining them costs more attention than the reassurance they buy. Avoiding that outcome is less about features than about deciding, before you start, which questions the portal exists to answer and refusing to let it answer any others.
Two questions, and no more
A retained client logging in wants to know what is happening now and what you need from them. A portal that answers those two well will be used. A portal that also offers dashboards, historical reporting, a file archive and a message board will be maintained for a while and then quietly stop being accurate, which is worse than not having it, because an out-of-date portal actively misleads. Deciding to answer two questions is the discipline that keeps the thing alive.
Maintenance has to be a by-product
If keeping the portal current is a separate task on somebody's list, it will lose to client work every time. The portals that survive are the ones where the practice's normal working actions update the client view as a side effect: marking something delivered, requesting an asset, changing a status. Judge client portal software for agencies on that mechanism specifically, because it is the difference between a portal that is true and one that was true in March.
Branding matters more here than elsewhere
An agency's client sees the portal as part of the agency's work, so a portal carrying a vendor's name and colors undercuts the impression the agency is being paid to make. White labeling is not vanity in this context, it is the product looking like it belongs to you. It is also worth checking how far it goes: a logo in the corner is common, while the domain, the emails the portal sends and the login page are what clients actually notice.
Questions people ask about client portal software for agencies
Why do agency client portals get abandoned?
Because keeping them accurate becomes a separate task that loses to client work. Portals survive when normal working actions update the client view as a side effect rather than requiring a second pass.
What should the portal show a retained client?
What is happening now and what you need from them. Resist adding reporting and archives; they are the parts that go stale first and take the portal's credibility with them.
How important is white labelling?
For agencies, more than for most. The portal reads as part of your work, so the domain, the sending address and the login page matter as much as a logo in the corner.