{Spam?} in subject ???

[Lupker]

Hi all,

I've migrated from Plesk 8.2 to 9.5.4. All went well, but I believe te SPAM protection is a little off at the moment.
I am using Spam Assassin, which is configured correctly (add the ***SPAM***) to the subject of my mails when they're marked as spam.

But I also receive and send mail which are marked as: {Spam?}

Does anyone know what program is responsible for this?

I am using: DomainKeys spam protection (both on) / SPF spam protection (include:spf.trusted-forwarder.org) and DNS blackhole lists (zen.spamhaus.org;dnsbl.njabl.org)

I've tested my own email software (Outlook 2007), which does not contain any extra anti-SPAM software.

Any clue?

gr,
Mark