Bounced Mail -- Delayed mail Exchange 5.5

[BabylonDrifter]

Hi I have recently upgraded our companies ISP from a 1/4 T1 to a Full T1. I have also changed ISP carriers and installed a PIX firewall. I am running NT 4 with Exchange 5.5. DNS is hosted localy and all ports are open to the email server.

The issue is emails sent to us are usually delayed, it is like they try to deliver but bounce and eventualy when the ISP retrys the email they get delivered. I see this especially when mail is sent from MSN. I see email delivering 1 hour to 1 day later after orginaly sent. I have been told that the issue may be that our server can't handle all the mail being sent to it at the new ISP speed. IS that possible ?? My memory is a little low and it does have a 10 mbs NIC, but the server is a dual PII server with plent of HD space. Internet access is great as well as sending email. We have about 125 users.

Anyone can you help??? Any exchange settings I can check, tests to narrow the problem?

I am still wondering if it could be DNS or the PIX firewall. I have mostly ruled these out since if there was a problem with DNS or the Firewall we should not get any email.

Thanks in advance for any advice.

 

[yizhar]

HI!

Check the DNS MX records for your domain name.
(use NSLOOKUP or sites like

http://www.samspade.org)

The lowest MX number (which means highest priority) should match with your Exchange server.

There are several other things to test and try.

With the PIX you can:
Debug using SYSLOG or internal "logging buffer" level 5-7
Try "no fixup smtp 25". The default "fixup smtp 25" works fine with Exchange servers, but you can disable it for the test and put it back again.

Give more info:
What PIX version?
Can you post partial configuration?
What are the DNS MX records?
Is there a Mail Relay in the middle?
Is the local DNS server the primary or secondary DNS server for your registered domain name (not recommended unless properly configured and managed)?
If the PIX is blocking DNS requests from the Internet to your internal DNS server it may cause such problems.
Best solution in many cases - let ISP handle registered DNS zones. Use internal DNS servers for internal clients only.

A test to narrow the problem - send email to IP address
name@x.x.x.x
(you might need to configure exchange to accept these addresses)

Bye


Yizhar Hurwitz

http://come.to/yizhar

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

 

[BabylonDrifter]

Hi thanks for the info!

I was browsing the PIX forum and saw the no fixup smtp command as well.

I tried the command "no fixup smtp" and it seems to work like a charm.
Should I have ented the command "no fixup smtp 25"??????

I am not exactly why this fixes the problem. I guess I need to research that command a little more.

Thanks for you help -- would have never caught it on my own.