That means it is the Internet Mail provider which is doing the detection (and also indicates spamhunter doesn't use a proxy). As far as I'm aware it should be set to No (I don't use this function), but some say yes, you can test both theories but I think start with no.
One of the issues is silent mode sends to the chest (it doesn't delete), but emails once in the chest can't be restored as a) there is no location to restore, e.g. inbox and b) it might corrupt the .dbx file if it knew where to restore it to.
I also don't know what form (file type) the email would be stored in the Chest as when saved from OE they are given, .eml file type, I don't know if this happens when sent to the Chest. You could check the virus chest Infected Files section and see how it is stored.
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As Pondus mentions about spam filtering as email server level, I will say that downloading email to then filter it really is a pointless exercise as you have to download 'all' email spam included to filter it. That is why I like the way MailWasher works.
MailWasher doesn't download the complete email to do its analysis, it only downloads the headers, a small part of the body, it doesn't download images or attachments and it views what is downloaded in text only. Based on this I personally don't feel that any negligible risk worth scanning duplication, that is why I exclude it from scans, but the choice is yours.
I run MailWasher first it flags all spam for deletion (you can add more if suspect), when you click Process it deletes the emails flagged from the server and calls your email program to download the remainder. On dial-up this saves me lots of time by not having to download all email and avast isn't finding suspect/infected emails.