I have been trying to setup Exchange 2016 for few days. everything is working perfectly. emails are working locally but sending emails from gmail and other outsiders does not work. i have setup my DC with this domain name "foo.local" and my email domain is "foo.us" out Exchange is hosted behind the firewall. and all necessary ports are being forwarded and tested specially 25

now i have setup everything properly. MX, autodiscover, mail.foo.us etc. even test from https://testconnectivity.microsoft.com/ (outlook connectivity seems pass) (but fail with inbound smtp email saying "The connection was established but a banner was never received."

i can exchange emails b/w local account just fine. when i telnet from any local PC to server i see this banner. 220 mail.foo.us Microsoft ESMTP MAIL Service ready at Mon, 9 Apr 2018 01:02:24 -0700

but when i telnet to my server from external IP. or from internet Trying 108.x.x.148... Connected to mail.foo.us. Escape character is '^]'.

(the upper massage shows no banner)

"default frontend" Connector is set with listening on All IPs and providing annonymus access to outsider. but still no luck please help.

  • firewall, either yours, or something upstream. – Jacob Evans Apr 11 '18 at 4:10

The only thing it could be on Exchange is the remote IP address range. That needs to be set to allow connections from all IP addresses - which is the default. Other than that, it is unlikely to be an Exchange issue. I would be looking at your firewall. Even if you didn't have anonymous enabled, you would still get the banner, because it would connect. No banner means the connection isn't being made to Exchange.

  • Make sure that your firewall isn't trying to do anything "smart" with the SMTP protocol. Cisco ASA for example, do some sort of "SMTP fixup" that breaks things, more often than not. – mfinni Apr 9 '18 at 14:15

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