[SOLVED] switched ISPs now outgoing mail times out connecting to server

[jptech]

We were using ma bell dsl before. Everything worked great.

Yes, I have a split DNS setup. There is a firewall in between our mail server and router. Yes, it worked fine before the switch.

yes, we have a PTR record setup.

I can send mail to some domains. When I try sending to a major ISP, the connection times out. The client has a lot of customers who use AOL and trying to send mail to AOL, times out.

I've tried connecting to their mail server via terminal and it just times out as does a ping.

Please help me troubleshoot this issue.

[raj]

hi..i dont know if you have connetivity problem or PTR..

do you have SNAT setup behind firewall? because if you dont then you firewall IP is what is going out and you may have PTR to your mail server ip.
check that and see what public IP is showing up in the headers to the ISP were you can get email.
if its your firewall IP then fix your PTR and check at the following link if your IP resolves.

http://postmaster.aol.com/tools/rdns.html


all the above is only for RDNS test/fix..if you have any other prob then please post the maillogs.

Raj

[jptech]

I do have snat.

there is only one public IP. the mail server is behind a nat router and snat firewall. now, this was working before the ISP changed. The ISP assures me the router is setup properly. I can receive email fine.

the aol RDNS tool shows a valid PTR matching my FQDN.

I'm really starting to believe it's a network issue related to someone else's firewall (eg. the ISP).

[jptech]

after much troubleshooting, I've determined that postfix is not looking up mx records. issue is still not resolved.

[phoenix]

after much troubleshooting, I've determined that postfix is not looking up mx records. issue is still not resolved.

How have you determined that?

[jptech]

determined that using dig.

the issue was really that postfix wasn't performing DNS lookups.

The outgoing mail would time out to any domain whose mailserver had a different IP than it's domain A record.

The enable DNS lookups was checked in the global settings. It was unchecked in the server settings.

I checked it in the server settings. The issue is now resolved.


Just as a side note, all console troubleshooting returned the global settings. The server settings were not returned. This severely hampered my troubleshooting.