I got this error when i try testing if smtp sender actual working! but i got this: ERROR: An error occurred while attempting to establish an SSL or TLS connection. This usually means that the SSL certificate presented by the server is not trusted by the system for one or more of the following reasons: The server is using a self-signed certificate which cannot be verified. The local system is missing a Root or Intermediate certificate needed to verify the server's certificate. A Certificate Authority CRL server for one or more of the certificates in the chain is temporarily unavailable. The certificate presented by the server is expired or invalid. It is also possible that the set of SSL/TLS protocols supported by the client and server do not match. See https://github.com/jstedfast/MailKit/blob/master/FAQ.md#SslHandshakeException for possible solutions. is possible to fix this problem?

smtp test error:

ProsameOG

I got this error when i try testing if smtp sender actual working! but i got this:
ERROR: An error occurred while attempting to establish an SSL or TLS connection.
This usually means that the SSL certificate presented by the server is not trusted by the system for one or more of
the following reasons:

The server is using a self-signed certificate which cannot be verified.
The local system is missing a Root or Intermediate certificate needed to verify the server's certificate.
A Certificate Authority CRL server for one or more of the certificates in the chain is temporarily unavailable.
The certificate presented by the server is expired or invalid.
It is also possible that the set of SSL/TLS protocols supported by the client and server do not match.
See https://github.com/jstedfast/MailKit/blob/master/FAQ.md#SslHandshakeException for possible solutions.

is possible to fix this problem?

aaPanel_Kern

ProsameOG
try:
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

If the display is not OK, please re-apply for SSL

Unable to send dkim headers
Troubleshoot log /var/log/rspamd/rspamd.log
Prompt for permission issues:
2022-04-20 00:27:56 #1363(rspamd_proxy) <6795e9>; proxy; dkim_module_load_key_format: cannot load dkim key /www/server/dkim/xx.com/default.private: cannot map key file: '/www /server/dkim/xx.com/default.private' Permission denied

Set 640 to 644, then restart rspamd to send emails to view the email source code, please replace xxx.com with your domain name.

chmod 644 /www/server/dkim/xx.com/default.private systemctl restart rspamd

Use this website to check whether the records of DKIM and SPF are correct?
https://www.dmarcanalyzer.com/dkim/dkim-checker/
https://dnschecker.org/spf-record-validation.php

Check the mail score and troubleshoot according to its error message
https://www.mail-tester.com/

Check blacklists
https://mxtoolbox.com/

Sending to gmail needs to configure SSL, do DKIM, SPF, it is best to let the network provider make the PTRRDNS record of ip