Problem with sendmail 8.13.7

[Paul Howarth]

Stefan Kuhlemann wrote:
> Paul Howarth schrieb:
>> Stefan Kuhlemann wrote:
>>> Hi  mailinglist
>>>
>>> I have a strange problem with sendmail 8.13.7. (Fedora Core 5)
>>>
>>> Sendmail is not able to send out any mail's. But: other smtp-hosts 
>>> are able to contact and deliver mails to this sendmail. The acutal 
>>> configuration did work until the last update via yum (which included 
>>> the sendmail update).
>>>
>>>
>>
>> Broken firewall rules perhaps?
>>
>> Any SELinux errors in the logs?
>>
>> Paul.
>>
> 
> Already checked the firewall rulesets before.  Also no SELinux errors.
> 
> even more strange - today around 10:00 o'clock the sendmail started to 
> work normal until 16:00 o'clock. (with nothing changed since sunday 22:00)
> 
> My feelings tell me that the reason might be some strange 'ill-broken' 
> firewall network stack or some weird netwok communication issues (like 
> the 'fun' with the ECN-flag some years ago)

TCP Window Scaling perhaps?
http://kerneltrap.org/node/6723

Paul.