Square bracket triggered an Virus Warning

[slcmarco]

I received a text only email that had some square brackets in the subject line.  That triggered a "Virus Alert".
After testing a little I realized that an email with just a [ in the subject line, triggers the alert.

[DavidR]

Sorry to spoil your theory but there is something more that that. I have just sent a test email, This [ is a [test] with lots of [square brackets] and avast didn't bat an eyelid either sending or receiving.

I also replied and changed the subject to just a single left [ square bracket, no problem sending or receiving either.

What is your email client ?
What is the sensitivity of the Internet Mail provider (Normal is the default) ?