## TL;DR
Rerun the Exchange security update from an elevated prompt with Exchange services stopped by setup itself, or stop them and the IIS worker processes manually first and disable antivirus scanning of the Exchange folders during install, because error 1603 here is the installer failing on locked, running services. Prove it on one failing machine before rolling it to the rest of machines in the deployment, because this fault repeats identically wherever the same condition holds and a fleet-wide or batch-wide first attempt multiplies the damage when the diagnosis is wrong.

```text
exchange server security update setup failed error 1603 because exchange services were not stopped before install
```

## Use this when
- You see this exact error or symptom: exchange server security update setup failed error 1603 because exchange services were not stopped before install.
- The failure is in Windows Update, WSUS, SCCM / MECM or Intune servicing on the affected machines, and it repeats on the same action rather than happening once and clearing.
- Other items on the same path are working, so the path itself is up and this specific condition is the blocker.

## Not for this skill when
- A different error code, message, or tool is involved. Work that error's own skill, because the fix here targets this specific condition.
- The whole service or platform is down. Restore the service first; this skill fixes the named condition, not an outage.
- You cannot identify one affected item to test on. Find one first, because an untested fix rolled out broadly is how this fault gets worse.

## Steps
1. Confirm the fault on one failing machine first and capture the evidence before changing anything: check Windows Update history, the CBS and DISM logs, and the WSUS or SCCM console status for one failing machine, and record the exact error text, the record or host involved, and the time it happened. Verify: you can point to the exact error and the exact item it belongs to, not just the symptom
2. Rerun the Exchange security update from an elevated prompt with Exchange services stopped by setup itself, or stop them and the IIS worker processes manually first and disable antivirus scanning of the Exchange folders during install, because error 1603 here is the installer failing on locked, running services. Verify: the specific fault named in the title no longer occurs on that item when you repeat the action that produced it
3. Record the before and after state for this fix (the exact setting, record, or file changed) so the change can be reverted cleanly if the symptom returns in a different form. Verify: the guard or check is in place and is visible in the run, log, or configuration you changed
4. Retest end to end: rescan and reinstall on one machine and confirm Update history (or the SCCM / Intune status) shows the update installed. Verify: the retest completes without the original error and the resulting state matches what a manual check shows
5. Roll the fix out to the rest of machines in the deployment in the same way, watching the first few for the same error, and note the root cause and the change in the run or incident record. Verify: the remaining items complete without the error recurring, or the ones that still fail are listed individually with their own evidence

## Variant phrasings
### error 1603 fix
The verbatim error or code phrasing for this fault in Windows Update; the fix is the same one in the steps above.
### exchange server security update setup failed error 1603 because
The full symptom phrasing as it appears in the console, log, or report where this failure surfaces.
### how to fix exchange server security update setup failed error 1603
The how-to phrasing for the same fault; start with the TL;DR fix, then work the steps in order.

Compatibility: Windows 10 and 11, Windows Server 2016 and later, WSUS, SCCM / MECM, Intune, DISM and the Microsoft Update Catalog as named in the title.

## Why it happens
This fault happens because the fault sits at a boundary between two systems, each of which reports its own side as healthy, so the evidence has to be lined up on both sides to see it. In this case the condition is the one named in the title, in Windows Update, WSUS, SCCM / MECM or Intune servicing on the affected machines: the receiving or acting side reports the failure faithfully, but the underlying state (a record, a setting, a credential, a file, or a mapping) does not match what that action assumes. Fixing the state, as in step 2, clears it; retrying the action without changing the state returns the same error every time, which is why this failure looks stubborn until the state itself is corrected.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_PeXZVm3m8wew9iCC9NlPkQ