DooMFeaR's questions

I got a problem with Modem Manager GUI in Ubuntu 22.04 LTS. It was running fine for few weeks and then suddenly it didn't launch anymore. I don't have any clue why, I didn't changed any setting of it. Can anyone help me out with this one? This is the output of sudo modem-manager-gui

    (modem-manager-gui:6269): GLib-CRITICAL **: 13:57:14.869: g_strrstr: assertion 'haystack != NULL' failed
Connection manager: Network Manager >= 0.9.0
Modem manager: Modem Manager >= 0.7.0

(modem-manager-gui:6269): GLib-CRITICAL **: 13:57:19.047: g_strrstr: assertion 'haystack != NULL' failed
Segmentation fault at address: 0x20
Stack trace:
1. /lib/x86_64-linux-gnu/libglib-2.0.so.0(g_bit_lock+0x50) [0x7f2f1f610540]
2. /lib/x86_64-linux-gnu/libglib-2.0.so.0(g_bit_lock+0x50) [0x7f2f1f610540]
3. /lib/x86_64-linux-gnu/libglib-2.0.so.0(g_variant_n_children+0x1d) [0x7f2f1f68a37d]
4. /usr/lib/x86_64-linux-gnu/modem-manager-gui/modules/libmodcm_nm09.so(+0x3bc0) [0x7f2f1c455bc0]
5. modem-manager-gui(mmguicore_connections_enum+0x6d) [0x55feed031d4d]
6. modem-manager-gui(+0x4a520) [0x55feed052520]
7. modem-manager-gui(mmguicore_devices_open+0x1c0) [0x55feed036f90]
8. modem-manager-gui(+0x415d2) [0x55feed0495d2]
9. modem-manager-gui(+0x4a7a2) [0x55feed0527a2]

I got a problem with my Dell E6230 Mobile Broadband connection in Ubuntu MATE 20.04. My laptop has a SIM card slot and also I have a SIM in it which has an internet plan active. Tested in Windows 10 and works ok. Laptops broadband card is a Dell DW5560. Trying to connect in the network manager shows that Mobile Broadband is not enabled. I created a connection using my SIM operator settings but still can't connect to it. Please see the screenshots attached.

Any help would be appreciated as I'm using my laptop sometimes away from an wifi connection and the mobile connection will be useful.

Thank you!!!

I'm reaching for your help because I tried everything I knew and cannot fix my issue. If I'am trying to use "apt-get install / apt-get update / apt-get purge" I am getting the following error:

 Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these.
The following packages have unmet dependencies:
 exim4 : Depends: exim4-daemon-light but it is not installed or
                  exim4-daemon-heavy but it is not installed or
                  exim4-daemon-custom but it is not installable
 exim4-base : Depends: exim4-config (>= 4.82) but it is not installed or
                       exim4-config-2
E: Unmet dependencies. Try using -f.

Of course I tried to run 'apt-get -f install' but that just pointed me to this error:

    apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
Correcting dependencies... Done
The following additional packages will be installed:
  exim4-config exim4-daemon-light
The following packages will be REMOVED:
  postfix
The following NEW packages will be installed:
  exim4-config exim4-daemon-light
0 upgraded, 2 newly installed, 1 to remove and 157 not upgraded.
3 not fully installed or removed.
Need to get 0 B/762 kB of archives.
After this operation, 1,498 kB disk space will be freed.
Do you want to continue? [Y/n] y
Preconfiguring packages ...
dpkg: warning: ignoring request to remove exim4-config, only the config
 files of which are on the system; use --purge to remove them too
Selecting previously unselected package exim4-config.
dpkg: regarding .../exim4-config_4.86.2-2ubuntu2.3_all.deb containing exim4-config:
 exim4-config conflicts with postfix
  postfix (version 3.1.0-3ubuntu0.3) is present and broken due to postinst failure.

dpkg: error processing archive /var/cache/apt/archives/exim4-config_4.86.2-2ubuntu2.3_all.deb (--unpack):
 conflicting packages - not installing exim4-config
Errors were encountered while processing:
 /var/cache/apt/archives/exim4-config_4.86.2-2ubuntu2.3_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

Any help would be appreciate! Thank you

dpkg --configure -a outputs this:

 `dpkg: error processing package exim4 (--configure):
 dependency problems - leaving unconfigured
Setting up libgnutls-openssl27:amd64 (3.4.10-4ubuntu1.5) ...
Setting up libc-dev-bin (2.23-0ubuntu11) ...
Setting up libc6-dev:amd64 (2.23-0ubuntu11) ...
Setting up postfix (3.1.0-3ubuntu0.3) ...

Postfix configuration was not changed.  If you need to make changes, edit
/etc/postfix/main.cf (and others) as needed.  To view Postfix configuration
values, see postconf(1).

After modifying main.cf, be sure to run '/etc/init.d/postfix reload'.

Running newaliases
Job for postfix.service failed because the control process exited with error code. See "systemctl status postfix.service" and "journalctl -xe" for details.
invoke-rc.d: initscript postfix, action "restart" failed.
● postfix.service - LSB: Postfix Mail Transport Agent
   Loaded: loaded (/etc/init.d/postfix; bad; vendor preset: enabled)
  Drop-In: /run/systemd/generator/postfix.service.d
           └─50-postfix-$mail-transport-agent.conf
   Active: failed (Result: exit-code) since Wed 2019-06-05 16:10:42 CEST; 20ms ago
     Docs: man:systemd-sysv-generator(8)
  Process: 17094 ExecStart=/etc/init.d/postfix start (code=exited, status=1/FAILURE)

Jun 05 16:10:41 mail postfix[17190]: See http://www.postfix.org/COMPATIBILITY_README.html for details
Jun 05 16:10:41 mail postfix[17190]: To disable backwards compatibility use "postconf compatibility_level=2" and "postfix reload"
Jun 05 16:10:41 mail postfix[17094]: /usr/lib/postfix/sbin/post-install: Error: /etc/postfix/postfix-files is not a file.
Jun 05 16:10:41 mail postfix/postfix-script[17207]: warning: unable to create missing queue directories
Jun 05 16:10:41 mail postfix/postfix-script[17208]: fatal: Postfix integrity check failed!
Jun 05 16:10:42 mail postfix[17094]:    ...fail!
Jun 05 16:10:42 mail systemd[1]: postfix.service: Control process exited, code=exited status=1
Jun 05 16:10:42 mail systemd[1]: Failed to start LSB: Postfix Mail Transport Agent.
Jun 05 16:10:42 mail systemd[1]: postfix.service: Unit entered failed state.
Jun 05 16:10:42 mail systemd[1]: postfix.service: Failed with result 'exit-code'.
dpkg: error processing package postfix (--configure):
 subprocess installed post-installation script returned error exit status 1
Processing triggers for libc-bin (2.23-0ubuntu10) ...
Errors were encountered while processing:
 exim4-base
 exim4
 postfix
`

I am running a Postfix - Dovecot - MySQL mail server on my personal Ubuntu dedicated server which I'm hosting it in my home.

Everything is working amazing except the fact that I am getting loads of incoming connection that I can see in /var/log/mail.log and these connections are coming from different IPs all over the world.

It looks like I'm getting DDoS'd and when the connections are kicking in, my internet connection drops for few seconds then it goes back on. It looks like someone is trying to take down my mail server.

Can anyone give me an idea how can I stop this? How can I improve the security of my Ubuntu dedicated machine? Any other advice that you guys can provide? I'm kinda new at this and Google didn't solve my problem.

I've made an email server on Ubuntu 12.04 using postfix, dovecot and roundcube as an web interface. Sending and receiving mails from Yahoo works fine (well, to be honest with a delay of 5 minutes, I don't know why...), but when I'm trying to send an email to my gmail address, I get this error:

 I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<[email protected]>: host gmail-smtp-in.l.google.com[2607:f8b0:4001:c0d::1a]
    said: 550-5.7.1 [2602:ff62:104:10c::] Our system has detected that this
    message does 550-5.7.1 not meet IPv6 sending guidelines regarding PTR
    records and 550-5.7.1 authentication. Please review 550-5.7.1
    https://support.google.com/mail/?p=ipv6_authentication_error for more 550
    5.7.1 information. 201si4583487ioc.208 - gsmtp (in reply to end of DATA
    command)

Can anyone give me some ideas? What I'm doing wrong? What about the delays that I'm encountering when sending and receiving from Yahoo!?

Cheers!