Send mail wrong name?

Hi,

I'm running Zimbra 8.0.3 with the latest Zextra's. And i have a problem, when i send an e-mail from my computer, the reiceiver sees "From : Dennis Brouwer", when i send an e-mail from the webmail, the receiver sees "From : Dennis Brouwer" BUT when i use my mobile phone (HTC One, Android), the receiver sees "From : mail". Mail = the username. How can i fix this?

Regards,
Dennis Brouwer