Linux ssmtp error Cannot open smtp.gmail.com:587

I can not route may emails vie gmail.com. I use ssmtp facility. My config files in /etc/ssmtp are

root:yyyyy@gmail.com:smtp.gmail.com:587
maciek:yyyyy@gmail.com:smtp.gmail.com:587

and ssmtp.conf:

rewriteDomain=gmail.com
root=yyyyy@op.pl
maciek=yyyyy@op.pl
hostname=yyyyyy@gmail.com
UseTLS=YES
UseSTARTTLS=YES
AuthUser=yyyyy@gmail.com
AuthPass=MyPass
FromLineOverride=YES

So I try:

# mail yyyyy@orange.pl
Subject: ddd
ddd
.
EOT
# send-mail: Cannot open smtp.gmail.com:587

Nothing block the traffic to gmail server as shown below:

$ telnet smtp.gmail.com 587
Trying 173.194.70.108...
Connected to smtp.gmail.com.
Escape character is '^]'.
220 mx.google.com ESMTP n1sm56130900eep.20 - gsmtp
ehlo
250-mx.google.com at your service, [83.25.153.55]
250-SIZE 35882577
250-8BITMIME
250-STARTTLS
250-ENHANCEDSTATUSCODES
250 CHUNKING
quit
221 2.0.0 closing connection n1sm56130900eep.20 - gsmtp
Connection closed by foreign host.

Logs from my system journalctl:

Dec 11 22:45:55 piotr sSMTP[7571]:
Creating SSL connection to host Dec 11 22:45:55 piotr sSMTP[7571]:
SSL not working: certificate verify fail...0) Dec 11 22:45:55 piotr sSMTP[7571]:
Cannot open smtp.gmail.com:587

No other MTA agent is installed on this computer (like sendmail). So what I am configuring wrong?