False positive on LF_QUEUE_ALERT?

[logout]

Since last night we've been receiving hourly alerts that LF_QUEUE_ALERT is higher than 400, but every time I check the mail queue there's only 5-10 messages in it.

I've checked the /var/spool/exim* directories and same thing.
I've checked /var/log/messages and see no evidence of spam.
I've checked WHM mail server statistics also.

Any ideas please?

[logout]

The alerts were coming from an old virtual machine that has accidentally been powered on. Doh!