hostname for sqwebmail

["marek cermak" <marasan@post.cz>]

Hi all
I use sqwebmail as a webmail application, everything works fine
except sending mail. The problem is with domain after '@'
character. Sqwebmail adds only hostname but not full FQDN. In
documentation I have found that the name after '@' can be
configured in file called 'hostname' located in data directory of
sqwebmail application. I don't know, where is the correct
location. I've tried severe locations but without success. So
what location is correct ?

Thanks
Marek Cermak