Redmine

Hi,
I'm a bitnami redmine server on aws.
I'm trying to create a crontab for receive imap.
if i try to exec command on terminal all function without problem.
the same command executed with a crontab don't function.
how can help me?

this is my command:
/opt/bitnami/apps/redmine/htdocs/bin/rake -f /opt/bitnami/apps/redmine/htdocs/Rakefile redmine:email:receive_imap RAILS_ENV="production" host=imap.gmail.com port=993 ssl=1 username=xxx@gmail.com password=xxx project=prova tracker=errore allow_override=tracker,priority unknown_user=accept no_permission_check=1

this is my crontab:
*/2 * * * * /opt/bitnami/apps/redmine/htdocs/bin/rake -f /opt/bitnami/apps/redmine/htdocs/Rakefile redmine:email:receive_imap RAILS_ENV="production" host=imap.gmail.com port=993 ssl=1 username=xxx@gmail.com password=xxx project=prova tracker=errore allow_override=tracker,priority unknown_user=accept no_permission_check=1

thanks.
l.