Puzzles with Mac Mail

I used to have very few addresses in the address book. Most of the addresses, once used, remained in the memory. So much so, that if I'd have several addresses for one person, all would show for me to select, once I started typing a name.

Some years ago I remember reading about how to fix this, never worked. But I think that it went away with the new Mac or new OS (High Sierra).

Anyhow, several months ago I got a new iMac. As soon as I set it up I could not get into my email. So I called Apple, with permission to get into my computer the rep found that I had to addresses: one for comcast.net, the other called High-Speed something. The rep deleted the high speed one (with about 300 emails, not a major loss, really), and everything has been fine.

All of a sudden, within the past two weeks, I realized that I can no longer contact people with whom I communicated just weeks ago. So I thought that until now the memory worked but no longer. And now I have to find them.

But I think that there is a different reason. On my dock there is an icon for Apps and on occasions I get a note for an update which I usually ignore, choosing something like "turn on notification," or something.

A few weeks ago I thought what the hell, let it update.

The next day, when I turned on my iMac (I always turn it off at the end of the day, including the power strip), I had to wait for an"update" which took forever. Spouse, with the MacBook says it happens all the time.

And whatever that update was, I think that it erased the memories of addresses which were not in the address book.

Does this sound crazy?