Outlook keeps showing error messages: general troubleshooting order

My Outlook throws a different error every few days. Sometimes send receive failures, sometimes a data file warning, once a crash on startup. Each time I search the exact code and apply a random fix.

Is there a sensible order to troubleshoot Outlook generally instead of chasing individual codes forever?

There is, and the order matters because each layer depends on the one below it. Random error hopping usually means one underlying fault expressing itself differently, most often a damaged data file or a bad add-in.

1

Add-ins first: run outlook.exe /safe from Win+R. Stable in safe mode means an add-in is guilty. Disable all under File, Options, Add-ins, then re-enable one per day until the errors return.

2

Data file second: run SCANPST.EXE from C:\Program Files\Microsoft Office\root\Office16 against every PST and the OST. Repeat the scan until it reports no errors, big files often need two or three passes.

3

Profile third: create a fresh profile from Control Panel, Mail, Show Profiles and run on it for a few days. Profiles quietly accumulate corruption over years and a rebuild resets that layer.

4

Office itself last: Online Repair from Programs and Features, which replaces every program file. Only reach this step if the first three did not stop the errors.

Keep a note of each error code and date while you work through the layers. If errors persist past step four, that history plus Event Viewer entries under Windows Logs, Application narrows it fast, and at that point the suspects are outside Outlook: antivirus mail scanning, a failing disk or a server side mailbox problem.

Safe mode was stable so I started with add-ins. An old PDF plugin was the source of at least two of the errors. Three weeks clean now, this checklist should be pinned.