Back into the discussion... I have had no problems since mid-January, but they are back.. In January, I let the emails download, and went through and weeded all of the old ones out... twice.
Then about a week ago, Outlook lost contact with my Main Identity, and built a new one (Identity 1). It had asked me to rebuild my Identity, but I got that sorted out with no problems.
Then it did again yesterday, but there was no new Identity 1. I fixed that (went back to the last backup). A few hours later, Outlook decided to download all my emails while I was actually working. (I think I had switched over from another application, but Outlook was running in the background.) I have just re-deleted all the extras AGAIN.
Another symptom is that often when I try to select a message in Outlook, it flips me over to Finder, and when I go back to Outlook, it repeats the behaviour. At that point, the only fix is to Restart.
Are these all connected? Who knows. My ISP (yes, they said it was them... see earlier) is of course out-to-lunch on this one.
Thinking about switching email clients, but it seems that other clients (other than perhaps gmail) are as bad. Thoughts on this last point?