RBL Strangeness

[Pete]

I have had soke compliants about false positives so i checked the logs
and find a bunch of email stopped because of reaching the spam score,
but reached thye spam score from being listed in sorbs, dnslbl, spamcop

These 3 had listed our countries largest ISPs mail gateways - it seems.

(i asume that these 3 list the originating mail server/gateway no email
addresses)

Can the above happen do to a failing of my mailscanner machine, a
failing in DNS or do these lists sometimes briefly list addresses? Eg
the day before and the day after the same servers were not getting hit
in those lists.

This is strange and hard to explain (which i have to) when i dont really
understand what could have happened - can anyone confirm if this
behaviour is normal?