Have problem installing Roundcube (SMPT can't connect)

[Matseoi]

Hello,
I have a problem when I am installing Roundcube with RoundcubeMail-1.2.1-complete.tar.gz.
But the test SMTP config says:

Trying to send email...
SMTP send:  NOT OK(Connection failed: Failed to connect socket: fsockopen(): unable to connect to ssl://mail.mydomain.com:587 (Unknown error))

At the same time, there is no problem with IMAP:

Connecting to ssl://mail.mydomain.com...
IMAP connect:  OK(SORT capability: yes)

I have tried to use the command line to send an e-mail:

Code Select Expand

echo 'test' | mailsend [email protected]
I can receive it on Gmail.

I tried through telnet command to test:

[root@mail ~]# telnet mail.domain.com 587
Trying xxx.xxx.xxx.xxx...
Connected to mail.burger-think.com.
Escape character is '^]'.
220 mail.burger-think.com ESMTP Postfix
^]
telnet> quit
Connection closed.
[root@mail ~]# telnet mail.mydomain.com 993
Trying xxx.xxx.xxx.xxx...
Connected to mail.burger-think.com.
Escape character is '^]'.
^]
telnet> quit
Connection closed.

Also, there is the log from /var/log/maillog:

Jun  2 12:17:28 mail postfix/smtpd[18857]: warning: connect to private/policyd-spfo: No such file or directory
Jun  2 12:17:29 mail postfix/smtpd[18857]: warning: connect to private/policyd-spfo: No such file or directory
Jun  2 12:17:29 mail postfix/smtpd[18857]: warning: problem talking to server private/policyd-spfo:
No such file or directory
Jun  2 12:17:29 mail postfix/smtpd[18857]: NOQUEUE: reject: RCPT from

More information:
PHP version 7.4.6
MariaDB 10.3
nginx version: nginx/1.14.1

Anyone can help?
Thank you.

[Matseoi]

Thank everyone who wants to help. And I have solved the problem. It is because I have to use the SSL SMTP port: 465. instead of 587