The body of the messages in kmail is empty, i receive only the subject of the messages.
I have a gmail imap account

I think that the problem comes from gmail because i saw double messages with empty body (in the browser gui) ... i will confirm

Yes, it was a gmail problem, this time was nt kmail's fault !!!

I don't know if it is a kmail problem finally. Today everything work fine in gmail, may be even when kmail is closed the imap is synchronized ? and probably a problem caused during the synchronization ? I had a duplicate blank message for every message. I will check again this evening at home

It is a problem with kmail. When i turned on my computer i have again duplicate blank messages in gmail
I deleted everything about akonadi in my home (for a xx time) and now i dont have the problem any more....

tired with akonadi, nepomuk etc...

i have again the problem: https://bugs.kde.org/show_bug.cgi?id=304741
now it is impossible to use kmail.

The cause was the spam filter, see the bug report above for more informations