The strangest problem I've ever seen


Well-Known Member
Sep 4, 2002
Just moved an account from an older Linux box to a new FreeBSD machine. Customer puts in a ticket to complain about her email not working. No problem, I think to myself... pretty common stuff with server migrations and customers that just need to alter a setting or two.

From my last ticket response to the customer:

1. Your email worked (ie downloaded to Outlook Express) immediately before we moved your account to a new server.

2. We've demonstrated that email is going to the new server. Evidence of that:
A. I've verified that our servers are reporting the correct IP address for your mailserver and your domain.
B. You've verified that you can ping [your domain] at the correct IP address.
C. You can log in to webmail with no issues and get email sent to your domain.
D. We've watched email be delivered via the exim mainlog.

3. I have created an account using your credentials and mail server names in Outlook Express and have been able to download copies of your email (while leaving copies on the server so you don't lose anything).

4. You have no issues with any portion of your site except the ability to receive email via the POP3 protocol, even after deleting and recreating the account in Outlook Express.

If we hadn't gone to the lengths of deleting and recreating the account, I'd say the only option open to us was that you had your POP3 server set to the IP address of the old server. Having eliminated that as a possibility, I'm afraid I really don't know what else to look at. We've checked logs, IP's, tested every facet of the system and it all comes back working for me, but not for you.

So... I'd love to hear any and all theories on this one... I'm completely stumped. Probably something simple... it is 5am and I've been on this for about 4 hours now.


Aug 3, 2004
if it's this serious and hard to find out then your client will have to use a packet sniffer :) That way you can check that 1. outbound packets go to the right pop3 server (and port), and 2. you can follow what commands are being sent and which one is the one that causes it to fail. I bet it's such a stupid thing that you always overlook :)


Dec 5, 2002
I've seen similar problems, and there were 2 causes.

1. The clients PC cached the old IP address for a domain. Resolved it by opening a DOS window (command prompt) and having them type

ipconfig /flushdns

2. Another client had a entry in their hosts file for the domain linking it to the old IP address. The hosts file is in the c:\winnt\system32\drivers\etc directory. It is easiest to open a command prompt and edit it with the dos edit command. The file may be located elsewhere depending on the windows install they have. They can do a search for hosts and find it.


Well-Known Member
Jan 17, 2003
I have had this problem before.

It resolves itself in time but the only way his emails start working right away is by making him use the server IP as incoming and outgoing mailserver.


Well-Known Member
Oct 31, 2001

1) duplicate ip, didn't remove the ip from the old server

2) router arp issue, have data center clear the arp cache on your router.