Usually, POPFile will classify a message, change the subject line and/or insert the X-Text-Classification header, and then hand the message on to your mail client. It's still the same message though, and it may contain web bugs or exploits that cause the preview function of your mail client to do something really nasty. For example, spammers may put some code in the HTML that lets them know you have received their email and thus, they should keep sending you more spam.
If you want to avoid that, you have two options: Get another mail client or use POPFile's quarantine function. On the buckets tab in the POPFile UI, you can turn quarantine on or off for each bucket separately. If POPFile classifies a message to a bucket that has quarantine turned on, POPFile will create a new email and add the original email to the new one as an attachment. The classified email is thus… well, quarantined.
When an email is quarantined, the new mail will let you safely “preview” some basic information about the quarantained email without having to open it. You will find the 'Original From', 'Original To' and 'Original Subject' of the quarantined mail, and the first 20 words that are found in the original mail. This way you can examine the quarantined mail without really having to open it.
Here's an example:
POPFile has quarantined a message. It is attached to this email. Quarantined Message Detail Original From: "Newsletter" <NOV-News2@newsletter435.cjb.net> Original To: "" <firstname.lastname@example.org> Original Subject: Don't Wait ( Corrected Link ) To examine the email open the attachment. To change this mail's classification go to http://127.0.0.1:8080/jump_to_message?view=popfile12353=2.msg The first 20 words found in the email are: This is multi part message in MIME format EMP Newsletter Reduce your debt and stop harassing phone calls without taking