Thanks for the reply Shell,
The fix you suggested relates to roundcube, I'm using the latest rc2 which I believe has been fixed.
I'm finding more and more of this as I progress, my server is in Brazil, South America. I travel a lot between North America and Europe as well and all regions I go takes me in different timezones.
I don't think the problem I posted above is true (relates to qmail), if I use a local application (evolution, thunderbird,etc.) this does not happen.
To sum all up, I still don't have an answer
I'll keep studying the problem...