@phenomlab I use two email clients… I tried to use a single one, but it was not possible due to my “clean inbox” strategy that I adopted over the years… so I use Apple Mail and Thunderbird…
I -also- have many separate email addresses (ashamed to write it down the count )… I combine all important ones under Apple Mail… And these are important personal and work emails and I keep this inbox clean (as much as possible). I read the email (if nothing needs to be done, archieve it) and tag it… When I am done, I archieve it… And I tag it if necessary…
And I mainly use Thunderbird for my two separate outlook/hotmail accounts… These are for “spammy” or frequent unimportant emails… Unfortunately there is no way for me to get away from them. So, for these email accounts, I do not even display the number of emails on the client, because it is full of spam that I will not read … I use outlook account for this purpose because Microsoft sucks at identifying real/spam emails…