Sendmail On CentOS 7.7

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CentOS 10 Comments

Hi All,

I am ‘trying’ to set SMART_HOST in sendmail to point to SMTP-relay.gmail.com but when looking at the /var/log/maillog its going to mx203.inbound-mx.net.
[192.110.255.243],

why???

my line from sendmail.mc define(`SMART_HOST’, `smtp-relay.gmail.com’)
I did make in /etc/mail and service sendmail restart

This is the only SMART_HOST in the config file. I started with the default CentOS 7.7 sendmail.mc and have not added anything else. just changed teh SMART_HOST.

Why is mail relay to mx203.inbound-mx.net ????

Nov 22 08:16:00 lsi001 sendmail[9286]: xAMDFxlA009286: touser.someone@gmail.com, ctladdr=root (0/0), delay:00:01, xdelay:00:01, mailer=relay, pri0197, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (xAMDFxjQ009287 Message accepted for delivery)
Nov 22 08:16:00 lsi001 sendmail[9289]: STARTTLS=client, relaymx203.inbound-mx.net., version=TLSv1/SSLv3, verify

10 thoughts on - Sendmail On CentOS 7.7

  • I would start by looking at the .cf file to make certain that it got written out correctly. You should find lines like:

    # “Smart” relay host (may be null)
    DSsmtp-relay.gmail.com

    If that looks right, then see what happens when you do dns queries for “smtp-relay.gmail.com” on that machine.

  • Great thought to check the generated file. It looks OK.

    grep gmail sendmail.*
    sendmail.cf:DSsmtp-relay.gmail.com sendmail.cf.bak:DSsmtp-relay.gmail.com sendmail.mc:define(`SMART_HOST’, `smtp-relay.gmail.com’) dnl

    host SMTP-relay.gmail.com smtp-relay.gmail.com has address 64.233.176.28
    smtp-relay.gmail.com has IPv6 address 2607:f8b0:4002:c02::1c

    service sendmail restart again – and same behavior going to relay
    203.inbound-mx.org

    Jerry

  • That is weird.. and from all the other posts I could find on google about this domain not good. I am not sure who ‘owns’ this domain but it only shows up in malware posting and similar spaces. And here is where:

    [smooge@smoogen-laptop ~]$ host -t MX SMTP-relay.gmail.com.com smtp-relay.gmail.com.com mail is handled by 10 mx203.inbound-mx.org. smtp-relay.gmail.com.com mail is handled by 10 mx203.inbound-mx.net.

    so something is adding another .com to your domain lookup. I would check the resolv.conf, your dns server or the configs elsewere

  • What does getent hosts SMTP-relay.gmail.com show? What does your hosts line in /etc/nsswitch.conf show?

  • .w SMTP-relay.gmail.com.com

    smtp-relay.gmail.com.com has address 79.124.78.105
    smtp-relay.gmail.com.com has address 79.124.78.101
    smtp-relay.gmail.com.com mail is handled by 10 mx203.inbound-mx.net. smtp-relay.gmail.com.com mail is handled by 10 mx203.inbound-mx.org.

    inetnum: 79.124.78.0 – 79.124.78.255
    descr: BlueAngelHost Pvt. Ltd country: BG => Bulgaria

    created: 2016-02-17T14:40:17Z
    last-modified: 2018-07-17T00:58:15Z
    source: RIPE

    org-name: BlueAngelHost Pvt. Ltd org-type: OTHER
    person: David John address: house 173. street, 4, E-block, ferozpur Road, Lahore, Pakistan phone: +14074597822 => “407 is principally Orlando, Florida.”

    Looks dodgy !

  • and, of course…

    $ host SMTP-relay.gmail.com smtp-relay.gmail.com has address 74.125.142.28
    smtp-relay.gmail.com has IPv6 address 2607:f8b0:400e:c08::1c
    $ whois 74.125.142.28
    …

    NetRange: 74.125.0.0 – 74.125.255.255
    CIDR: 74.125.0.0/16
    NetName: GOOGLE
    NetHandle: NET-74-125-0-0-1
    Parent: NET74 (NET-74-0-0-0-0)
    NetType: Direct Allocation OriginAS:
    Organization: Google LLC (GOGL)
    RegDate: 2007-03-13
    Updated: 2012-02-24
    Ref: https://rdap.arin.net/registry/ip/74.125.0.0
    ….

  • maybe add a ‘.’ to the end of the host name? that prevents it from applying assumed default domains to it

    like this:

    define(`SMART_HOST’, `smtp-relay.gmail.com.’) dnl

  • See below:

    getent hosts SMTP-relay.gmail.com
    2607:f8b0:4002:c06::1c SMTP-relay.gmail.com

    # /etc/nsswitch.conf
    #
    # An example Name Service Switch config file. This file should be
    # sorted with the most-used services at the beginning.
    #
    # The entry ‘[NOTFOUND=return]’ means that the search for an
    # entry should stop if the search in the previous entry turned
    # up nothing. Note that if the search failed due to some other reason
    # (like no NIS server responding) then the search continues with the
    # next entry.
    #
    # Valid entries include:
    #
    # nisplus Use NIS+ (NIS version 3)
    # nis Use NIS (NIS version 2), also called YP
    # dns Use DNS (Domain Name Service)
    # files Use the local files
    # db Use the local database (.db) files
    # compat Use NIS on compat mode
    # hesiod Use Hesiod for user lookups
    # [NOTFOUND=return] Stop searching if not found so far
    #

    # To use db, put the “db” in front of “files” for entries you want to be
    # looked up first in the databases
    #
    # Example:
    #passwd: db files nisplus nis
    #shadow: db files nisplus nis
    #group: db files nisplus nis

    passwd: files sss shadow: files sss group: files sss
    #initgroups: files sss

    #hosts: db files nisplus nis dns hosts: files dns myhostname

    # Example – obey only what nisplus tells us…
    #services: nisplus [NOTFOUND=return] files
    #networks: nisplus [NOTFOUND=return] files
    #protocols: nisplus [NOTFOUND=return] files
    #rpc: nisplus [NOTFOUND=return] files
    #ethers: nisplus [NOTFOUND=return] files
    #netmasks: nisplus [NOTFOUND=return] files

    bootparams: nisplus [NOTFOUND=return] files

    ethers: files netmasks: files networks: files protocols: files rpc: files services: files sss

    netgroup: nisplus sss

    publickey: nisplus

    automount: files nisplus sss aliases: files nisplus