lowering power use on my Kogan Agora Laptop, by reverting to an older graphical user interface, I have now increased the performance of email by switching from the default "Evolution" email package to the less featured Mozilla Thunderbird.
Evolution has calendar functions which I did not want and so just added to the complexity of the interface. It also tended to spend a lot of time downloading copies of email over my slow wireless link. Thunderbird just does email, but does it much quicker. So far I have not worked out how to switch off the Evolution icon from the top of the screen. When I am confident Thunderbird is working properly, I will un-install Evolution, which hopefully will remove all trace of it.