If I recall correctly (I no longer use this option...), you uncheck the
option in the Options menu, and this instance will no longer receive the
new files. So they will open in a new window. You can re-check the
option in the instance you want to receive the next files (only one
instance should get the option).
--
Philippe Lhoste
-- (near) Paris -- France
-- http://Phi.Lho.free.fr
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Regards Frank
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Sent from my Android phone with K-9 Mail. Please excuse my brevity.