I think I need IP Spoofing
I have been dealing with this for several months now, and I am running out of ideas...
- Company-A has an internal mailserver working as expected.
- Company-B has itīs mail service hosted by its ISP (ISP-B).
- EMails from Company-A can not be delivered to the mailserver of ISP-B .(meaning that I know of at least 3 domains hosted by ISP-B to whom mail canīt be delivered).
- I can not establish a telnet connection from Company-A to ISP-Bīs smtp server, from any of the systems on c-Aīs LAN.
It either times out of stays forever waiting for the connection to initiate.
I can do it from 3rd party IPs of diff ISPs.
I canīt find someone else using c-Aīs ISP to run a test.
- No explanation about why I canīt telnet to the smtp is given.
- ISP-B dismisses the issue by simply claiming there are no blockings in his side that could be causing this.
- All sorts of tests and verification were made in Company-A, and everything looks good. This includes online tests, RBL checks, rDNS, etc. etc.
- All I can think of at this stage, is that ISP-B is blocking us, be it by our IP, IP block, or because of some particular hardware/software combination they might have (re: http://support.microsoft.com/kb/895857). No answers received about that either.
- My very last idea is to spoof the IP address and see what happens if we were on a different IP / IP block ????.
All I need is to find out if the telnet session is prompted properly or even prompted at all...
Suggestions greatly appreciated!
Thanks in advance.