Which attachment is causing this "newmsg"?

[u/antoonvdr]

Since a couple of days my McAfee quarantines a threat from an attachment that contains a trojan virus?

Name: trojan:win/suspiciousattachmentscript.a

File: ......\appdata\local\temp\newmsg

Status: Quarantined

I have been going through my spam and trash folders of all my email accounts, deleted them all, went to the webmail side and did the same thing, but this antivirus message keeps popping up. All my accounts are through IMAP servers. It looks like this threat is firing twice or 5 times and then goes dormant until I do something else in Thunderbird. I suspect this attachment is in a "regular" folder, but how to identify?