Brazilian trojan horse query

[#1]

Recently I’ve had several one line e-mails (with zip attachments purportedly giving full details) from Brazil asking me to change a room reservation. An online search reveals that this is a common scam and that such attachments are likely to contain ‘trojan horses’, yet according to Plusnet they have been scanned and are free of viruses and malware whilst my own AV software also detects nothing amiss.
Needless to say I delete them unopened but is this not a bit odd?

[#2]

You can try marking them as spam using Webmail. Whilst not an immediate solution, it's likely to do some good over time.

[#3]

It's possible that the zip file attached is clean (so it passes AV checks) but links within it go to malicious sites. Even if malware content from the page is blocked the email address they used is identified as a good prospect for future scams.