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  • Difference in EHLO response between IPv4 and IPv6

    From Grant Taylor@21:1/5 to All on Thu Mar 25 12:08:29 2021
    Hi,

    I've run into the following head scratcher:

    I'm seeing different responses to EHLO depending if the client is
    connected with IPv4 vs IPv6.

    Both DaemonPorts have the same configuration save for the expected
    Address, Family, and Name.

    I'm at a loss as to where to start looking for this different behavior.

    Does anyone have any ideas what to check first?

    #[user@REDACTED:~]% nc -4 REDACTED 25
    220 REDACTED ESMTP Sendmail 8.15.2/8.15.2; Thu, 25 Mar 2021 17:58:17 GMT
    ehlo REDACTED
    250-REDACTED Hello REDACTED [REDACTED], pleased to meet you 250-ENHANCEDSTATUSCODES
    250-PIPELINING
    250-EXPN
    250-VERB
    250-8BITMIME
    250-SIZE
    250-DSN
    250-ETRN
    250-STARTTLS
    250-DELIVERBY
    250 HELP
    rset
    250 2.0.0 Reset state
    quit
    221 2.0.0 REDACTED closing connection

    #[user@REDACTED:~]% nc -6 REDACTED 25
    220 REDACTED ESMTP Sendmail 8.15.2/8.15.2; Thu, 25 Mar 2021 17:58:35 GMT
    ehlo REDACTED
    250-REDACTED Hello REDACTED [REDACTED] (may be forged), pleased to meet you
    250 ENHANCEDSTATUSCODES
    rset
    250 2.0.0 Reset state
    quit
    221 2.0.0 REDACTED closing connection

    Aside: I'm also perplexed by the "(may be forged)" in that response.
    Both forward and reverse DNS are functioning correctly on the host and
    the Internet at large.



    --
    Grant. . . .
    unix || die

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Grant Taylor@21:1/5 to Grant Taylor on Thu Mar 25 14:35:04 2021
    On 3/25/21 12:08 PM, Grant Taylor wrote:
    I'm seeing different responses to EHLO depending if the client is
    connected with IPv4 vs IPv6.

    It seems as if adding the `delay_checks' FEATURE may have solved (or at
    least worked around) my problem. But I don't understand why.

    Aside:  I'm also perplexed by the "(may be forged)" in that response.
    Both forward and reverse DNS are functioning correctly on the host and
    the Internet at large.

    I still don't know what to make of the "(may be forged)" message.



    --
    Grant. . . .
    unix || die

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)