mail server MX lookup fails through PIX

[welk]

Running a Groupwise 6.5 mail server (on W2K) on the inside (private) network which reports an MX lookup failure when attempting to send mail out going throught the PIX 501 firewall. This is a new installation of the firewall. If the firewall is bypassed, things seem to work okay.

Other applications requiring name resolution work fine from the server (a W2K box) through the firewall (Web browsing, nslookup, etc.). Incoming mail is not affected (port 25 is mapped to the server).

The PIX configuration is, with substitions for security, as follows:

PIX Version 6.2(2)
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password encrypted
passwd encrypted
hostname xyz
domain-name thedomain.com
fixup protocol ftp 21
fixup protocol http 80
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol ils 389
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol smtp 25
fixup protocol sqlnet 1521
fixup protocol sip 5060
fixup protocol skinny 2000
names
access-list acl_out permit icmp any any
access-list acl_out permit tcp any any eq smtp
pager lines 24
logging buffered debugging
interface ethernet0 10baset
interface ethernet1 10full
mtu outside 1500
mtu inside 1500
ip address outside xx.xx.xx.238 255.255.xxx.xxx
ip address inside 192.168.x.x 255.255.xxx.x
ip audit info action alarm
ip audit attack action alarm
pdm location 192.168.x.x 255.255.xxx.xxx inside
pdm logging informational 100
pdm history enable
arp timeout 14400
global (outside) 10 interface
nat (inside) 10 0.0.0.0 0.0.0.0 0 0
static (inside,outside) tcp interface smtp 192.168.xxx.xxx.xxx smtp netmask 255.255.xxx.xxx 0 0
access-group acl_out in interface outside
route outside 0.0.0.0 0.0.0.0 xx.xx.xx.237 1
timeout xlate 0:05:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h323
0:05:00 si
p 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
aaa-server LOCAL protocol local
http server enable
http 192.168.xxx.xxx 255.255.xxx.xxx inside
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
floodguard enable
no sysopt route dnat
telnet 192.168.xxx.xxx 255.255.xxx.xxx inside
telnet 192.168.xxx.xxx 255.255.xxx.xxx inside
telnet timeout 15
ssh timeout 5
dhcpd address 192.168.xxx.xxx-192.168.xxx.xxx inside
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd auto_config outside
dhcpd enable inside
terminal width 80
--------------------


With out success we also attempted with the additional configuration lines of
access-list acl_out permit tcp any any eq domain
access-list acl_out permit udp any any eq domain
access-list acl_in permit tcp any any eq domain
access-list acl_in permit udp any any eq domain


While the DNS records point somthing like:
mail.thedomain.com MX 10 xxx.xxx.xxx.238

the reverse lookup of xxx.xxx.xxx.238 shows something like:
abcd-ef-xx-xx-xx-238.xyz.ab.com

While one might be suspicious that the problem is the mail server finding a non-matching reverse lookup, I'm inclined to think that if that were the problem the failure would still occur when the PIX firewall is not in place. However, the outgoing mail does not fail if the PIX is removed.

Any suggestions? (Thanks)

KL

 

[yizhar]

HI.

> logging buffered debugging
So - what relevant syslog messages can you catch?

> Any suggestions?
Meanwhile, you can configure your ISP SMTP server as a "smart host" in your mail server configuration, so all outgoing mail will be forwarded to ISP, and your server will not need to do DNS MX lookup for outgoing mail.

You should also check the mail server configuration and manuals regarding that issue.


Yizhar Hurwitz

http://come.to/yizhar

http://teachers.sivan.co.il/yizhar

 

[welk]

For anyone else it may help, the problem below was resolved with the documented IDENT protocol problem. See

http://www.cisco.com/warp/public/110/2.html