I am seeing the same issue, but I can't find that it is a firewall issue. Below is my pix config anything look wrong there? My ISP says it is related to us not having a PTR record with them.


fixup protocol dns maximum-length 512
fixup protocol ftp 21
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol http 80
fixup protocol pptp 1723
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sip 5060
fixup protocol sip udp 5060
fixup protocol skinny 2000
fixup protocol smtp 25
fixup protocol sqlnet 1521
fixup protocol tftp 69
names
name 192.168.0.21 MAIL
access-list acl_out permit icmp any any echo-reply
access-list acl_out permit icmp any any echo
access-list acl_out permit icmp any any time-exceeded
access-list acl_out permit tcp any any eq www
access-list acl_out permit tcp any any eq pptp
access-list acl_out permit tcp any any eq smtp
access-list acl_out permit tcp any any eq imap4
access-list acl_out permit tcp any any eq 7071
access-list acl_out permit tcp any any eq 993
access-list acl_out permit tcp any any eq 587
access-list acl_out permit tcp any any eq 465
pager lines 24
mtu outside 1500
mtu inside 1500
ip address outside xxx.xxx.xxx.xxx 255.255.255.252
ip address inside 192.168.0.1 255.255.255.0
ip audit info action alarm
ip audit attack action alarm
pdm location SBS 255.255.255.255 inside
pdm location 192.168.0.0 255.255.255.255 inside
pdm location WWW 255.255.255.255 inside
pdm logging informational 100
pdm history enable
arp timeout 14400
global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
static (inside,outside) tcp interface smtp MAIL smtp netmask 255.255.255.255 0 0
static (inside,outside) tcp interface www MAIL www netmask 255.255.255.255 0 0
static (inside,outside) tcp interface imap4 MAIL imap4 netmask 255.255.255.255 0 0
static (inside,outside) tcp interface 7071 MAIL 7071 netmask 255.255.255.255 0 0
static (inside,outside) tcp interface 993 MAIL 993 netmask 255.255.255.255 0 0
static (inside,outside) tcp interface 587 MAIL 587 netmask 255.255.255.255 0 0
static (inside,outside) tcp interface pptp MAIL pptp netmask 255.255.255.255 0 0
static (inside,outside) tcp interface 465 MAIL 465 netmask 255.255.255.255 0 0