On 28 Jun 2016, at 2:39, Michael Fox wrote:
I also tried port 25 and 587 from a separate machine that has an IP
address
in mynetworks. In that case, EHLO is not even recognized:
telnet <ipaddress> 587
220 <myhostname> ESMTP Postfix (Ubuntu)
EHLO client.example.com
502 5.5.2 Error: command not recognized
HELO client.example.com
250 <myhostname>
QUIT
FWIW: that's sometimes a symptom of a broken firewall that thinks it
knows SMTP but does not, with the canonical example being a Cisco PIX in
its default configuration.
That particular form doesn't look exactly like PIX-mangling, and I don't
think PIX (or its ASA spawn) interfere with port 587 by default, so it's
probably something else, but that something else may be something
claiming to be providing you network security while in the process
directly breaking the spec for port 587 mail submission. A port 587
service that doesn't support EHLO is just antique SMTP on a weird port.
