SMTP problem after a reinstall

I moved my w2k DC, with Exchange 2k and ISA server on it, to a different
motherboard.

To have the ACPI functional, I had to reinstall w2k, networking and IIS. 
After the reinstall of Xch2k, uninstall/reinstall of the ISA sp1,
everything was working, but outgoing mail was delivered with a delay.

Suddenly, it stopped delivering mail at all. All messages reside in SMTP
queues.
What could be missing? Does anyone have an idea? Thanks.


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