[cobalt-users] Strange sendmail reports -- email attack?

["Brian M. Rahill" <brian@xxxxxxxxxxxxxxxxxxxxxxx>]

Hi All,

Any idea what this log (see below) means.  I've got tons of them...this 
message is create something like every 30 seconds for days...

____________
Apr 20 18:59:31 admin sendmail[14980]: f3KMwAa14980: ruleset=check_mail, 
arg1=<asvdsign@xxxxxxxxxxx>, relay=IDENT:root@[202.161.150.2], reject=451 
4.1.8 <asvdsign@xxxxxxxxxxx>... Domain of sender address 
asvdsign@xxxxxxxxxxx does not resolve
____________

Is is some sort of email attack?

I've also been seeing some of these (2/hr)

_________
Apr 19 16:51:19 admin named[20848]: ns_forw: 
query(120.172.235.216.in-addr.arpa) All possible A RR's lame
__________


Any thoughts are much appreciated.

Thanks!

Brian