X-Authentication-Warning ???? How to fix this?

[Nexohrion (JeanPaul) (Webmaster AT Shizukana.net)]

Hi,

Can you tell me how to fix this error?

X-Authentication-Warning: xemmen.raisingfire.net: nobody set sender to
nexohrion at raisingfire.net using -f

I got banned in CBL because of this

I run IMAPD, POPA3D, and PostFix,
My mail scanner is ClamAV with Clamsmtpd.

I get this error only if I mail with squirrelmail
So this should be a sendmail error...

How can I fix this?

Regards, Nexohrion