I must admit, I wasn't using Maemo email client, because I did find it was simply unusable, at least with my GMail account.
I tried both POP3 and IMAP, but having about 25.000+ messages in my account, downloading just the headers was a job that the client simply couldn't manage.
Yesterday I knew about "recent mode" support in POP3, a functionality that GMail supports too. This mode allow you to download only last 30 days messages (in my case, no more than 1000) so the client can manage them without any problem.
All you have to do to enable this mode is put the "recent:" string before the username. For example: if your username is "firstname.lastname@example.org" you have to write "recent:email@example.com". Important: this mode only works with POP3, not with IMAP.
To conclude, let me say thank you to the kind guy who let me discover this mode. Thank you Sergio! Now there is another thing I can do with my tablet!