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Re: Postfix (Ubuntu 9.10 x64) said: 421 4.4.1 Connection timed out (in reply to end of DATA command)

From: Mihira Fernando (mihiratheacegmail.com)
Date: Fri May 28 2010 - 06:40:59 CDT


On Fri, 28 May 2010 14:41:46 +0300
"Ioannis Tsouvalas" <tsouvalasiatic.gr> wrote:

> reply
>
> Stan Hoeppner put forth on 5/28/201 5:42 AM:
>
> >The vmxnet 'NIC' is a virtual device, strictly a software driver.
> >The vmxnet driver communicates with the ESX kernel at the speed of
> >system memory, which on modern servers is over 10x faster than the
> >10 Gbe signaling rate. There is no such thing as "link speed" in
> >this scenario as the interfaces are all software. Ethernet link
> >speed, more correctly called a link pulse synchronization, is
> >generated by hardware devices called PHYs. Link pulse is a hardware
> >phenomenon. It doesn't exist in phantom software drivers, in this
> >case the vmxnet drivers.
>
> >Your issue is unrelated to the vmxnet "link speed" settings, unless
> >there is a bug in the vmxnet driver code. If you send an email from
> >an instance of Postfix running on a Linux guest to an instance of
> >Exchange running on a Windows guest, both guests running on the same
> >ESX physical machine, any communication between the two MTAs will
> >occur via direct memory copy. The data will never be sent to the
> >physical NIC in the server. The communication takes place through
> >the ESX virtual ethernet switch, which again is strictly software.
> >
> >--
> >Stan
>
>
> Stan thanks for the reply, as well as the insight regarding the
> difference between soft and hard nic devices. The only reason I'm
> pointing out the link pulse as well as the MTU, is that my search so
> far points me towards that direction. Now if there is a bug within
> the driver, then I guess more communication errors would have
> occurred, and the issue wouldn't be isolated on the smtp
> communication. That unfortunately, leads me back to where I started,
> without even some hope on getting closer to the solution.
>
> Looking forward to further insight,
> -
> Ioannis
>

Are there any firewalls between the Postfix and Exchange Server ?

Mihira.