Problem with SSL certificate and SMTP connection

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husamsamra
Posts: 1
Joined: Wed Jan 13, 2021 7:41 pm

Problem with SSL certificate and SMTP connection

Post by husamsamra » Wed Jan 13, 2021 7:59 pm

Hello
I have MailEnable premium installed on my server, and need to implement SSL certificate in order to use it with SMTP connections as usual.
After implementing the certificate to IIS and setting it in MailEnable server configurations, I couldn't connect to the server via secure connection using TELNET for example, instead of that I only get a black screen in CMD after calling telnet command on the port 587 enabled with SSL certificate.

You can try that like this:
telnet 52.255.201.160 587

If you try telnet with port 25 and (EHLO) command you can see STARTTLS supported in commands.

Any help with this issue?

Thanks.

Admin
Site Admin
Posts: 842
Joined: Mon Jun 10, 2002 6:31 pm
Location: Melbourne, Victoria, Australia

Re: Problem with SSL certificate and SMTP connection

Post by Admin » Wed Jan 27, 2021 4:06 am

If you have configured an SSL port for a service, you will only get a black screen when you use Telnet to connect to it. So it is indicating it is likely working. To test SSL ports you are best to use something like OpenSSL, which gives you a lot of ability to diagnose connections, make sure they are TLS 1.2, etc.

For example, you can check if a port is TLS 1.2:

openssl s_client -tls1_2 -connect 127.0.0.1:587

Or check STARTTLS works:

openssl s_client -starttls smtp -tls1_2 -connect 127.0.0.1:25

SantaPhil
Posts: 13
Joined: Wed Dec 18, 2019 8:16 pm

Re: Problem with SSL certificate and SMTP connection

Post by SantaPhil » Fri Feb 12, 2021 7:02 pm

I found this site very helpful in confirming that SSL and TLS are set up correctly. Found a few bugs the first time I used it.

https://www.checktls.com/TestReceiver

Click on the "More Options" to select a different port etc...

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