When I try to mark an email as spam using the link at the bottom of the email, i receive an error:
You must be on a trusted network to teach Antispam Engine!
This behaviour is by design since version 2.6 to avoid fraudolent bayesian poisoning actions from anuthorized people copying and pasting email strings.
You can disable this restriction under menù System->User Management by changing the option “Users can teach Antispam only from Trusted Net” to NO.
Otherwise if you only need a trusted subnet/host you can leave this option to YES and add the trusted network from menù System-Relay-Trusted Hosts.