Quoting Eric Messick:
> When I telnet to my own address, I get the 220 greeting immediately. When
> they try the sender verify, I give them at least a 30 second delay, and they
> close and fail the verify.
I have seen such behaviour with broken firewalls (somewhere on the way,
could be on yours or their side) which erroneously tried to handle tcp
window scaling (rfc 1323). Are they/you using Linux with kernel >
2.6.17? Then try "echo 0 > /proc/sys/net/ipv4/tcp_window_scaling". See
e.g.
http://kerneltrap.org/node/6723 for more information.
