Solved Certificate error on secure SMTP

[Elvin.H]

Hi all,

We're trying to configure custom SMTP server with SSL/TLS enabled ( using TCP 587 ) on Linux 3CX server, and when trying to test it gives error:
"An error occurred while attempting to establish an SSL or TLS connection. The server's SSL certificate could not be validated for the following reasons: The root certificate has the following errors: unable to get local issuer certificate."

The same SMTP settings work well on other 3CX server installed on Windows. We have installed mail server's certificate in trusted CA certificates on Linux server, but it didn't help.

Has anyone faced the same?

 

[YiannisH_3CX]

This error usually comes up when an intermediate certificate is missing so the TLS chain cannot be verified.

What Debian version are you using?

 

[Elvin.H]

This error usually comes up when an intermediate certificate is missing so the TLS chain cannot be verified.

What Debian version are you using?

Its version 9.9
I've manually installed intermediate and root ca certificates from /usr/local/share/ca-certificates/, with no results.

 

[Elvin.H]

Is there any way to bypass certificate checking? (I understand that it's not secure, but may be used as a last resort)

 

[VasilisV_3CX]

Hi @Elvin.H,

Being a premier customer I believe the best bet would be contacting your partner to investigate. In the interim may I suggest using the 3CX SMTP to ensure that everything is up and running?

 

[Elvin.H]

The issue is resolved.
The reason was that our mail server responses with different certificates on 443 and 587 ports. On windows it worked because the certificate for 587 is already trusted as signed by domain CA. On linux it worked after adding CA and SubCA certificates to trusted root CA store.

 

[YiannisH_3CX]

Glad to see that issue has been resolved and thank you for sharing your solution with the community.