One of my clients was using Outlook for his Gmail account. It worked fine for several years. Suddenly, it just stopped working. The Gmail servers began to reject his credentials. I logged onto his account, using the credentials he gave me and they worked. But those same credentials fail in Outlook 2010. I checked and double checked all the settings and found everything in order.
I repaired Outlook; I verified that POP was enabled on his PC. All the settings are correct (I've checked and double-checked them).
I’ve run out of ideas. Does anyone have any suggestions?