I was about to start a similar thread, I use ProfiMail on E90 and it have similar features as Thunderbird (multi-account, large attachment support, HTML emails, custom interval updates etc..) and this is really an important factor since I do a lot of office work via email and get huge attachments (mostly PDF schematics) that needs a short review and reply. Hopefully the default client on Maemo won't be so limited or slow as the built in Symbian client on E90.