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Thread: Leap 15.2 port 25 no longer accept remote connections

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  1. #1
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    Default Leap 15.2 port 25 no longer accept remote connections

    I recently build a brand new mail server with Leap 15.2

    I installed sendmail as MTA and enabled remote connections on port 25 using Yast and also checking that /etc/sysconfig/mail has the value:

    SMTPD_LISTEN_REMOTE="yes"

    and restarted sendmail.

    sendmail accepts connections on port 25 for the localhost but refuses it from the external interface. I have firewall and apparmor disabled (yes I do not need them, I have an enterprise class firewall).

    This works instead on a 15.1 server and on a 15.1 server that has been upgraded to 15.2.

    This is the nmap output on the local interface:

    # nmap -sS -O 127.0.0.1
    Starting Nmap 7.70 ( https://nmap.org ) at 2021-04-14 19:58 EDT
    Nmap scan report for localhost (127.0.0.1)
    Host is up (0.0000040s latency).
    Not shown: 991 closed ports
    PORT STATE SERVICE
    22/tcp open ssh
    25/tcp open smtp
    53/tcp open domain
    80/tcp open http
    119/tcp open nntp
    139/tcp open netbios-ssn
    443/tcp open https
    445/tcp open microsoft-ds
    873/tcp open rsync
    Device type: general purpose
    Running: Linux 2.6.X
    OS CPE: cpe:/o:linux:linux_kernel:2.6.32
    OS details: Linux 2.6.32
    Network Distance: 0 hops

    This on the external interface:

    # nmap -sS -O 192.168.0.4
    Starting Nmap 7.70 ( https://nmap.org ) at 2021-04-14 19:56 EDT
    Nmap scan report for smoke (192.168.0.4)
    Host is up (0.000049s latency).
    Not shown: 992 closed ports
    PORT STATE SERVICE
    22/tcp open ssh
    53/tcp open domain
    80/tcp filtered http
    119/tcp open nntp
    139/tcp open netbios-ssn
    443/tcp filtered https
    445/tcp open microsoft-ds
    873/tcp open rsync
    Device type: general purpose
    Running: Linux 2.6.X
    OS CPE: cpe:/o:linux:linux_kernel:2.6.32
    OS details: Linux 2.6.32
    Network Distance: 0 hops


    Has anyone experienced this issue and is there a way to enable remote smtp conncetions?

  2. #2
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    Default Re: Leap 15.2 port 25 no longer accept remote connections

    I don't have direct experience here, but just speculating that maybe examine /etc/mail/sendmail.mc and check the options there....you may need to comment out "DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')" as mentioned here...

    https://www.linuxquestions.org/quest...7/#post4248900

    Similar archived thread...
    https://opensuse.opensuse.narkive.co...ng-connections
    openSUSE Leap 15.2; KDE Plasma 5

  3. #3
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    Default Re: Leap 15.2 port 25 no longer accept remote connections

    Quote Originally Posted by deano_ferrari View Post
    I don't have direct experience here, but just speculating that maybe examine /etc/mail/sendmail.mc and check the options there....you may need to comment out "DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')" as mentioned here...

    https://www.linuxquestions.org/quest...7/#post4248900

    Similar archived thread...
    https://opensuse.opensuse.narkive.co...ng-connections
    No, that setting is not in the linux.mc (or sendmail.mc) Also trying the sendmail.cf that is working on the 15.1 and 15.1 that was upgraded to 15.2 and still isn't working.

  4. #4
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    Default Re: Leap 15.2 port 25 no longer accept remote connections

    Quote Originally Posted by cdieni View Post
    No, that setting is not in the linux.mc (or sendmail.mc) Also trying the sendmail.cf that is working on the 15.1 and 15.1 that was upgraded to 15.2 and still isn't working.
    Any particular reason for choosing sendmail over postfix?
    openSUSE Leap 15.2; KDE Plasma 5

  5. #5
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    Default Re: Leap 15.2 port 25 no longer accept remote connections

    Quote Originally Posted by deano_ferrari View Post
    Any particular reason for choosing sendmail over postfix?
    I have been administering Unix systems for over 30 years (since PDP-11) and I have always used sendmail. I know how to program rulesets and I would like to continue doing so and not having to go rewrite all in a totally different MTA I do not know. I know Postfix is a much easier MTA to manage, but as I was mentioning earlier, I do believe OS developers should not push one application over another, just because they like it, or at least if they believe openSUSE should run postfix as an MTA _only_, then they should remove sendmail from the distribution entirely (so that people like me can then choose a different Linux distribution that supports what we like to use). If not, then they should properly support it.

  6. #6
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    Default Re: Leap 15.2 port 25 no longer accept remote connections

    I do not quite understand you. I nowhere read that "OS developers" (do you mean Linux Kernel, Linux in general or openSUSE developers) are pushing anything upon you.

    I only only read a few fellow openSUSE users, and probably also MTA users, who ask you why you prefer the one over the other. Probably because they have good experiences with the one you do not use, and thus could better help you whith what they think is a good (maybe even better) product. They do not "push" you, but are trying to access the background of you and your problem with the idea that people that understand each others motives and goals do have a more fruitful communication.
    Henk van Velden

  7. #7
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    Default Re: Leap 15.2 port 25 no longer accept remote connections

    Quote Originally Posted by hcvv View Post
    I do not quite understand you. I nowhere read that "OS developers" (do you mean Linux Kernel, Linux in general or openSUSE developers) are pushing anything upon you.

    I only only read a few fellow openSUSE users, and probably also MTA users, who ask you why you prefer the one over the other. Probably because they have good experiences with the one you do not use, and thus could better help you whith what they think is a good (maybe even better) product. They do not "push" you, but are trying to access the background of you and your problem with the idea that people that understand each others motives and goals do have a more fruitful communication.
    And since they have asked I have given my opinion, I am sorry if you do not like it, but that is what I think. I never said they were pushing me in one direction or the other. What I said is that OS developers (meaning whoever put the 15.2 distribution together) if they want to have Postfix as a default MTA, that is fine. However, If they keep Sendmail as an alternative MTA they need to make sure it works in the exact same conditions as Postfix does (i.e., it accepts local and remote connections), so that fellow openSUSE users and MTA users, such as me, are not forced to move to Postfix if their Sendmail distribution ain't working anymore. If they cannot do that, then better to stop supporting it entirely, because as it is now, it is unusable. What I meant when I said they were pushing (and again to be clear NOT who asks me why I use sendmail, but who maintains the 15.2 distribution) is that by supporting one MTA correctly and the other not, indirectly one is been pushed to go for what works, even if he/she does not like/does not know it, has done a lot of work on the other and now is forced to migrate all of that work to a new one.

    In my opinion, a "better product" is most of the time a matter of preference. They both may do what they are supposed to do, but one may be preferred from another for different reasons, and most of the time it is personal (past experience, easy to configure and maintain, etc). In this case one fails to perform as expected, not because it is a worse product, but because of something else, and that is why I am asking for help.

  8. #8
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    Default Re: Leap 15.2 port 25 no longer accept remote connections

    Quote Originally Posted by cdieni View Post
    but who maintains the 15.2 distribution.
    They are not here.
    Henk van Velden

  9. #9
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    Default Re: Leap 15.2 port 25 no longer accept remote connections

    This works as intended on a 15.2 LiveCD or -NET install in a VM.

    Changing /etc/sysconfig/mail SMTPD_LISTEN_REMOTE="no" to SMTPD_LISTEN_REMOTE="yes", then restarting or starting sendmail makes it listen to 0.0.0.0:25.

    Have you altered the sendmail configuration files/templates or the systemd service file?
    .: miuku #suse @ irc.freenode.net

  10. #10

    Default Re: Leap 15.2 port 25 no longer accept remote connections

    I have not used sendmail for a long time but maybe you could execute /usr/sbin/config.sendmail. I think this script will create a new /etc/sendmail.cf from your new settings in /etc/sysconfig/mail. Then restart sendmail.
    I am not sure if this works correct when IPv6 is enabled for sendmail. Maybe you need to set SENDMAIL_USE_IPV6="no" in /etc/sysconfig/sendmail if sendmail complains for IPv6 related problems.

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