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You probably have to adjust your Terminal settings using Terminal --> Preferences --> Settings --> Advanced --> (un)check Delete sends Control-H To troubleshoot and see what your Backspace is actually sending, enable network data debug in your Telnet by: telnet set netdata o [the Windows server name or IP] Now all characters sent (back and forth) will ...


1

The first thing I would do before proceeding further would be to test port 25 end to end with a tool like netcat. The tool comes standard with most linux distros. For example on CentOS I would stop postfix to release port 25. Then I would start netcat like this: # nc -l 25 Then on the remote client I would start it like this: # nc {ip of remote ...


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According to the nmap docs: filtered Nmap cannot determine whether the port is open because packet filtering prevents its probes from reaching the port. The filtering could be from a dedicated firewall device, router rules, or host-based firewall software. These ports frustrate attackers because they provide so little information. Sometimes they respond ...


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That idiosyncratic and invalid EHLO argument "ylmf-pc" is a known fingerprint of a widespread spamming botnet known as "PushDo" (and sometimes alternatively "Cutwail"). As shown in your transcript, it is mostly trying password guessing to authenticate and send mail through your server. Keeping it from sending spam to or through your server is easy, because ...


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The helo name of the attacker is invalid (ylmf-pc) because it's neither a FQDN, nor resolvable via DNS, so you can easily get rid of it earlier, by blocking him after the invalid EHLO is sent. To do this with postfix, for example, do: smtpd_helo_restrictions = permit_mynetworks, check_helo_access reject_invalid_helo_hostname, reject_non_fqdn_helo_hostname, ...



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