mac_dolar
Refer to this article. You need the help of a server provider or network provider
https://en.wikipedia.org/wiki/Reverse_DNS_lookup

      aaPanel_Kern
      why I can send email from the webmail, but I can't send mail using SMTP, its shows this error below
      I have tried connecting using port 25, 587, 465 and yet the same error.. the domain.com is used to reference my domain name.

      Server: mail.domain.com
      User: user@domail.com
      Result: FAILED, code 3016: Failed to send command.

      Transcript:

      220 mail.domain.com ESMTP Postfix

      EHLO mail.domain.com
      250-mail.domain.com
      250-PIPELINING
      250-SIZE 102400000
      250-VRFY
      250-ETRN
      250-STARTTLS
      250-AUTH PLAIN LOGIN
      250-ENHANCEDSTATUSCODES
      250-8BITMIME
      250-DSN
      250-SMTPUTF8
      250 CHUNKING
      STARTTLS
      220 2.0.0 Ready to start TLS
      SSL negotiation failed, code 1: SSL module internal error.
      error:14077438:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert internal error
      AUTH LOGIN
      Failed to send command

      Operation completed: 10/27/2022 5:16:53 p.m.
      Elapsed time: 1.1 seconds

      1) Please what could be the problem?
      2) if possible, please can you give me your email address let me send you my panel login details so that you help me and configure the aapanel mailserver?

      thank you.

          mac_dolar
          Hello, please try to reapply for SSLs at the mail server. At the same time, check the postfix configuration, which can be viewed in the server status
          "mail.135mailtest.com" is replaced with your domain name
          Put:
          smtpd_tls_chain_files=/etc/ssl/private/ssl-cert-snakeoil.key,/etc/ssl/certs/ssl-cert-snakeoil.pem
          Change to:
          smtpd_tls_chain_files = /www/server/panel/plugin/mail_sys/cert/135mailtest.com/privkey.pem,/www/server/panel/plugin/mail_sys/cert/135mailtest.com/fullchain.pem
          Note to replace 135mailtest.com with your domain name.
          Also check /www/server/panel/plugin/mail_sys/cert/135mailtest.com/ for privkey.pem and fullchain.pem files
          You can use this command to check whether the correct SSL is configured
          openssl s_client -connect mail.135mailtest.com:587 -starttls smtp
          or
          openssl s_client -connect mail.135mailtest.com:465 -starttls smtp

              aaPanel_Kern
              please where can I locate this file below you said I should modify?
              smtpd_tls_chain_files=/etc/ssl/private/ssl-cert-snakeoil.key,/etc/ssl/certs/ssl-cert-snakeoil.pem

              I have tried to configure the mailserver many times, but it keeps on not working properly.
              Please wouldn't it be better I give you me aapanel login details so that you help me and configure the postfix mailserver?

              thank you.

                  mac_dolar
                  Hi, can you give us your aapanel information? The server makes a snapshot backup first, if possible, please send it to kern@aapanel.com.
                  It is recommended to fill in the following
                  Post link:
                  SSH IP address, account password and port:
                  aapanel login link address and account password:

                  No post link will not be able to know which user's information is

                      aaPanel_Kern
                      Please check the email, I have sent you the all the server information you requested.

                      Please let me know once the issue is solved!
                      Thank you so much.

                        10 months later

                        Hi, please check if mysql is running? can be found in the app store
                        Please check whether the database interface can add a test database?
                        Please check whether the user and password configured on the website are correct?

                        kloudboy

                          a year later
                          a month later

                          aaPanel_Jose I have tried your method. But after changing password, use can;t login to roubcube webmal anymore. Login failed.