Has the honourable (ha! Thunderbird insists I spelled this badly and one of its suggestions was 'unburnable' - awesome! and apt.) gentleman considered looking into automatically filtering his email? Good email clients and even some email providers allow you to simply and quickly create rules that can file/delete incoming mail and therefore save lots of time.
Gmail does this eminently and there is always the "all mail" feature in case something get mis-filed. I recently went through the process of creating filters on my Virgin Media (blueyonder to the old hands) account, which uses the gmail engine, and the result was nothing short of miraculous. I used to struggle under the weight of emails, now I hardly have to bother at all.
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