Your outlook profile got corrupted. First make a backup of your email in a PST file. Then in Control Panel -> Mail. Click on the profiles button. Delete your current profile and create a new one.
Is this a newly created profile or an existing one that used to work and now does not? Try starting outlook in safe mode. (start, run, type outlook /safe). If that works you may have some problematic add-ins. Disable them all and re-enable them one by one until you find the culprit.
And in the end …
Outbound (SMTP) mail settings had been “port 25 with no encryption”. That failed with the ambiguous error code. Setting SMTP to use port 587 and TLS seems to have resolved that.