> On Sun, May 14, 2023 at 08:36:38AM +0800, Tom Reed wrote: >> tcp 0 0 0.0.0.0:587 0.0.0.0:* >> LISTEN >> 32157/master >> >> >> And the telnet results: >> >> $ telnet 193.106.250.xx 587 >> Trying 193.106.250.xx... >> telnet: Unable to connect to remote host: Connection timed out > > So, it looks like it's not a LAN address. It's a mail server on the > public Internet? As in, your telnet client and your server are NOT > talking directly to each other over a straight ethernet connection? > There's routers and stuff in between them?
Yes. my mailserver is in NYC DC, and the client host is in Dallas DC. > > You'd need to investigate the possibility of a firewall-equivalent at > each hop along the way. > I may need tcpdump for watching the rst packages. Thank you Tom
