==== Required information ====
- iRedMail version (check /etc/iredmail-release):
- Linux/BSD distribution name and version:
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):
- Web server (Apache or Nginx):
- Manage mail accounts with iRedAdmin-Pro?
- Related log if you're reporting an issue:
======== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.2
- Linux/BSD distribution name and version: CentOS release 6.7 (Final)
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Apache 2.2.15
- Manage mail accounts with iRedAdmin-Pro? Nope
- Related log if you're reporting an issue: Down below
====

Hi guys,
I run CakePHP with Email-transport SMTP:
In app.php
'EmailTransport' => [
        'default' => [
            'className' => 'Smtp',
            // The following keys are used in SMTP transports
            'host' => 'smtp.domain.tld', (I´ve set my domain here)
            'port' => 25, (left this 25 as in Thunderbird it works with 25)
            'timeout' => 30,
            'username' => 'username', (yes, I set this)
            'password' => 'password', (this also)
            'client' => null,
            'tls' => true, (I set this to true)
        ],
    ],
The exact settings are working with Thunderbird, there I can send and receive mails flawlessly.

When registering a user internally a confirmation mail is sent via CakePHP but the app tells me this error:
SMTP server did not accept the connection or trying to connect to non TLS SMTP server using TLS.

I use the standard installation of iRedMail which runs fine aside my problem.
/var/log/maillog delivers:
Oct  2 17:57:23 v22015093023528042 postfix/smtpd[1930]: connect from 123.456.789.0.pools.vodafone-ip.de[1$
Oct  2 17:57:24 v22015093023528042 postfix/smtpd[1930]: lost connection after STARTTLS from 123.456.789.0$
Oct  2 17:57:24 v22015093023528042 postfix/smtpd[1930]: disconnect from 123.456.789.0.pools.vodafone-ip.d$

I tried it already with roundcube config.inc.php:
// SMTP
$config['smtp_server'] = 'tls://domain.tld';
instead of "tls://127.0.0.1"
Not working

Then I tried to open TLS1 and 1.1 in /etc/postfix/main.cf:
smtpd_tls_mandatory_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtpd_tls_protocols=!SSLv2,!TLSv1,!TLSv1.1,!SSLv3
Not working.

Now I don´t have a clue what to do. Thanks in advance