postfix/smtpd: warning: <ipaddr>: hostname <fqdn> verification failed

[Gavin McCullagh]

Hi,

on our v2.2.3 kolab install, we're getting regular messages like:

Jul 16 10:48:45 XXXXX <warning> postfix/smtpd[23939]: warning: 93.86.229.159: hostname 93-86-229-159.dynamic.isp.telekom.rs verification failed: Name or service not known
Jul 16 10:50:31 XXXXX <warning> postfix/smtpd[23939]: warning: 59.164.0.50: hostname 59.164.0.50.man-dynamic.vsnl.net.in verification failed: Name or service not known
Jul 16 10:53:16 XXXXX <warning> postfix/smtpd[23941]: warning: 77.75.100.210: hostname as100210.airspeed.ie verification failed: Name or service not known

As far as I can see, this is postfix warning of an incoming smtp
connections from hosts who have a PTR record, but that PTR record doesn't
have a corresponding A record.  Is that right?  

Does postfix reject that connection or does it just warn me of it?

Which entry in main.cf triggers this check?  Is this the kolab_smtpdpolicy
stuff?

Most of the warnings appear to be from hosts which look like they're in
dynamic ISP allocations.  These probably are SPAM bots, so this behaviour
seems reasonable.  I'd just like to understand it a little better.

Thanks in advance,
Gavin