Error HTTP 500 on fresh install with nginx

[topmktwww]

Folks, how are you?

I am having this problem, I can open the webmail site like http://webmail.mydomain.com but when i insert the user and password thta I created using the vimbadmin i get the error, when I click on login.
on thunderbird mozilla is working fine, no problems so far, but my clients wants to use on webmail system,

could you please help me this out?

many thanks

Robson

[SKaero]

What in the error log?

[topmktwww]

I am a newbie user, how can I see this log ?

thank you

[SKaero]

If its in Roundcube error log it would be in <RC root>/logs/errors otherwise it would be in the web server logs.