On Sun, 10 Sep 2023, Erwan David via Postfix-users wrote:
On Sun, 10 Sep 2023, postfix--- via Postfix-users wrote:
Try a telnet connection to those host (gmail/mail-tester) on 25 and see
who actually answers.
1) Send SYNs with varying TTLs to determine the number of hops to alleged
recipient MTAs based on the minimum value which elicits a SYN/ACK. Are
they all the same? Is it a low number?
This part can be done with traceroute or mtr command in TCP mode
Good point. The other test can be done with traceroute as well, by
specifying different ports. (Route and number of hops will typically be
the same for all ports on a host.)
Be sure to specify TCP (-T or --tcp).
--
Fred
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