Doing a proper SSL certificate configuration right is very important not only to the security or the server and website but could also have a very great impact on the performance of the Email server.

Therefore , it is best to confirm that the SSL for your SMTP,POP3 and IMAP is working correctly with the right SSL certificate configuration.

To confirm that the SSL is working correctly. follow the guidelines below;

For SSL on IMAP using port 993:

Therefore, connect to the mail server ,lets say for example "domain.com" using openssl, use the command below;

$ openssl s_client -showcerts -connect mail.domain.com:993

Upon running the above command, you are expected to get a positive response with the valid certificate which will be displayed. You will also see that IMAP courier is okay if everything is fine.

For POP3 Which uses Port 995 when SSL Mode is activated:

To connect to the mail server ,lets say for example "domain.com" using openssl, use the command below;

$ openssl s_client -showcerts -connect mail.domain.com:995

You can have a look at the output to see if you have got a valid certificate or not. If valid, you will get a positive response or an "OK".

For SMTP protocol which uses port 465 when in the SSL mode:

You can do a connection action to the mail server via openssl by using the command below;

$ openssl s_client -showcerts -connect mail.domain.com:465

In the same way as the other checks, you will see a positive output if the certificate is valid.

This check can also be replicated for SMTP on port 25 and 587. In this case, use the command below;

On port 25, use:

$ openssl s_client -starttls smtp -showcerts -connect mail.domain.com:25

While on port 587, use:

$ openssl s_client -starttls smtp -showcerts -connect mail.domain.com:587

Conclusion

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