I have recently set up our 2 front-end and SMTP servers in an MS NLB. I gave the NLB cluster the same IP as our original mail server to avoid changing any MX records or A records for the OWA. Everything works fine except for a strange problem for which I can find no defined errors.
To test the cluster I am using telnet on the port for the SMTP service (25). This connects fine every time from outside our organisation, but for some reason the ability to connect in this method internally is distinctly sporadic.
Can anyone shed any light as to why this might be happening, or at least somewhere that I can look to find out the errors?
Additionally, I have run Ethereal on a number of clients whilst attempting the connection tothe cluster and it seems that the cluster simply does not respond to some clients internally, despite the fact that the same client can ping the cluster and connections from outside the organsiation work fine. Also, clients that can't connect at one time seem to just start working with no changes being made.