Postmar integration problem

Your software
My Mautic version is:
My PHP version is: PHP Version 7.0.33
My Database type and version is:

Your problem
My problem is:
I am trying to connect postmar , I am using a API key in username and log in as it was said in many other topics here, but still I am getting the error,

please can anyone put a normal guide how to connect postmark to mautic

Unable to connect with TLS encryption Log data: ++ Starting Mautic\EmailBundle\Swiftmailer\Transport\PostmarkTransport << 220 p-pm-outbound04c-aws-euwest1c.smtpservice.postmarkapp.com ESMTP p-pm-outbound04c-aws-euwest1c >> EHLO 10.1.1.239 << 250-p-pm-outbound04c-aws-euwest1c.smtpservice.postmarkapp.com 250-PIPELINING 250-SIZE 20480000 250-VRFY 250-ETRN 250-STARTTLS 250-AUTH PLAIN LOGIN CRAM-MD5 DIGEST-MD5 250-AUTH=PLAIN LOGIN CRAM-MD5 DIGEST-MD5 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN >> STARTTLS << 220 2.0.0 Ready to start TLS !! Unable to connect with TLS encryption (code: 0)
++ Starting Mautic\EmailBundle\Swiftmailer\Transport\PostmarkTransport << 220 p-pm-outbound04c-aws-euwest1c.smtpservice.postmarkapp.com ESMTP p-pm-outbound04c-aws-euwest1c >> EHLO 10.1.1.239 << 250-p-pm-outbound04c-aws-euwest1c.smtpservice.postmarkapp.com 250-PIPELINING 250-SIZE 20480000 250-VRFY 250-ETRN 250-STARTTLS 250-AUTH PLAIN LOGIN CRAM-MD5 DIGEST-MD5 250-AUTH=PLAIN LOGIN CRAM-MD5 DIGEST-MD5 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN >> STARTTLS << 220 2.0.0 Ready to start TLS !! Unable to connect with TLS encryption (code: 0)

These errors are showing in the log:

Steps I have tried to fix the problem: