Linux/Sendmail problem points to kernel incompatibility on Dell Poweredge 1950

Greetings,

I have a user that complains that her messages are not getting to a particular outside user. I investigated the error message that said:

"Could not deliver the message in the time limit specified"

I investigated further to see if the destination email server was available from my email server by telneting to port 25 on the destination email server and I could not get a connection. My first assumption was that it was down, but just in case it was a firewall related issue, I checked from another server outside our network and was able to connect. I ran updates on the server, including the kernel and was able to finally connect, however when I issued an EHLO command, I got nothing, it just hung, but from other workstations and servers I was able to connect and issue an EHLO command.

All of the above describes FC6 on a Dell PowerEdge 1950. From a workstation (an old Dell GX1) running FC6, I have no problem with my telnet/EHLO test. So the problem appears to be specific to the PowerEdge 1950.

I decide to run further tests. I have another PowerEdge 1950 that I am planning on deploying in May, so I use it as a test bed. I install FC5 and the default kernel (kernel-smp.2.6.15-1.2054) has no problem with my telnet to port 25 and EHLO test. So I think, fine, I'll just get this FC5 box up to date and set it up as my email server. So I get it all up to date, try my test again, and I can telnet into port 25 of the destination email server but it hangs when I issue an EHLO command.

Obsessive at this point, I begin installing each revision of the FC5 kernel to see when it breaks and here is what I find:

Key = Kernel Version, Telnet to Port 25?, Issue EHLO?

kernel-smp.2.6.15-1.2054, ok, ok
kernel-smp.2.6.16-1.2080, ok, ok
kernel-smp.2.6.16-1.2096, ok, ok
kernel-smp.2.6.16-1.2107, ok, NO

So it is on kernel-smp.2.6.16-1.2107 that it breaks and it seems to be related only to my Dell PowerEdge 1950 server.

I realize that Fedora is unsupported on Dell PowerEdge servers, however, considering that RHEL 5 ships with kernel 2.6.18, the problem may be present there as well.

 

Does anyone else have a Dell PowerEdge 1950 server running either FC5 or FC6 (or perhaps RHEL 5) that would like to perform this telnet/EHLO test as well? I can give you the particular destination email server if interested.

Does anyone have any idea what is going on?

Grendelos