[CentOS] DHCP/DNS server for LAN with mainly Windows clients : Outlook Express vs. Webmail problem

[Alexander Georgiev]

2010/6/11 Niki Kovacs <contact at kikinovak.net>:
> Now the curious problem I have: IP addresses are attributed correctly,
> people can surf on the internet all right. But the only thing they can't
> seem to do is send mail with Outlook or Outlook Express. I have to
> revert to the ISP's DNS, but so I lose the benefit of local DNS. And I
> don't have the slightest clue as to why that is so.
>

Perhaps, they cannot resolve the IP address of their outgoing SMTP server?