Cannot telnet port 25 in windows server 2016 installed exchange 2016

Benard Mwanza 996 Reputation points
2021-11-30T05:26:17.33+00:00

I'm unable to telnet port 25 in windows server 2016 that has exchange 2016 installed.

I can telnet port 25 in another server running other exchange in the same network, but for this one am unable.

Windows firewall is disabled.
In edge Firewall the port is allowed.
I checked with netstat command for listening, and its showing listening

Note:
Outgoing traffic for that port is open, for example if run, telnet smtp.gmail.com 25, it returns well.

When i telnet localhost or 127.0.0.1, the IP of the server or the FQDN of the server, i get an error. Connection to host lost

What could be issue.

Windows Server
Windows Server
A family of Microsoft server operating systems that support enterprise-level management, data storage, applications, and communications.
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Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
7,227 questions
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4 answers

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  1. Andy David - MVP 138.6K Reputation points MVP
    2021-11-30T19:22:37.707+00:00

    Ok, no worries. Was the firewall enabled when you installed Exchange? It should be. Re-enable it and try again.

    Is there any 3rd party software installed? Are the receive connectors enabled? and no one changed the config?

    1 person found this answer helpful.

  2. Andy David - MVP 138.6K Reputation points MVP
    2021-11-30T12:33:13.223+00:00

    windows server 2019 that has exchange 2016 installed

    This is not a supported configuration! You need to remove Exchange and rebuild it

    Exchange 2016 is not supported on Windows 2019

    https://learn.microsoft.com/en-us/exchange/plan-and-deploy/supportability-matrix?view=exchserver-2019

    153609-image.png


  3. Andy David - MVP 138.6K Reputation points MVP
    2021-11-30T20:12:39.587+00:00

    Only if you changed the config of the allowed remote IPs - not a typical thing to do.

    I would disable Mcafee completely and try telnet on port 25 again, if re-enabling the Windows firewall doesnt work.

    Note that you need to exclude all the required dirs and processes if McAfee is not Exchange aware:

    https://learn.microsoft.com/en-us/exchange/antispam-and-antimalware/windows-antivirus-software?view=exchserver-2019

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  4. Limitless Technology 39,216 Reputation points
    2021-12-02T20:46:45.923+00:00

    Hi @Benard Mwanza

    Try checking out the below points which might be a potential cause for these issues.

    -The Firewall rules could be set explicitly. That may be one reason for not working for this particular server.
    -SMTP connection restrictions may also be a cause, check to make sure connections are allowed.
    -May also be an IP version issue, IPV6 works on 2012R2 and not in 2013.
    -Check the antivirus' firewall on the VM Host which might be blocking the ports.

    -------
    --If the reply is helpful, please Upvote and Accept it as an answer--

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