[Modsecurity] Squirrelmail "Forward" message does not work

[Roberto]

H,
I have mod_security installed and users can not use the
Forward
function in Squirrelmail 1.46 and they get:

----------------------------
Internal Server Error
The server encountered an internal error or misconfiguration and was unable 
to complete your request.

Please contact the server administrator, me at myemail and inform them of the 
time the error occurred, and anything you might have done that may have 
caused the error.

More information about this error may be available in the server error log.
----------------------------------------

In audit_log I have this:
---------------------------------
mod_security-action: 500
mod_security-message: Access denied with code 500. Pattern match 
"\\n[[:space:]]*(to|b?cc)[[:space:]]*:.*@" at ARGS_VALUES("body") [severity 
$"EMERGENCY"]

---------------------------------

Is this the problem?
What can I do?

Any help would be Great!

Thanks
Roberto