Antispam problem with ssl scanning

I've noticed a little problem with the antispam plugin on Outlook 2010. I'm not sure if it's a bug or if it's related to my settings.

I've noticed an icon which appears on some emails below the date/time details in the main email list. I've highlighted the icon in red in the screenshot below. I believe it means that the email hasn't been scanned. If I select an email with that icon, Outlook is unable to preview it and it skips to the next message. It will continue to skip messages until it reaches an email that doesn't have the icon.

The mail accounts in question use imap protocol and ssl.

If I go to the Antispam plugin on the ribbon bar, I can select to rescan all messages in the folder and the icon disappears and i'm able to browse through the emails without issue. When ssl scanning is enabled, everything works perfectly but i've read some threads where the general advice is to keep ssl scanning disabled.

Any suggestions please?

 

With which version of ESS does this issue occur? The icon on those emails is not a familiar one but based on your troubleshooting but it does indeed appear to be an issue with the antispam plugin. What Windows O/S is on this computer?

 

5.2.9.1 running on Windows 7 Ultimate x64.

Thank you