system
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I now realize why it showed up seemingly at random. I am running MailWasher in the background every 15 minutes. It fetches mail headers and sorts them according to Bayesian rules into friendly and blacklisted.
The icon is a nuisance and I prefer not to have it popping up and down all the time. I had it turned off in the previous installation and I still managed to be warned when mail had suspect content. I do not need to be advised from the tray.
Now that is turned off I am no longer pestered all the time.
Thanks for your assistance.