Thank you SKaero
We fixed the problem by following the suggestion in this link
https://www.roundcubeforum.net/index.php?topic=22035.0This is what we did in our RC config.inc.php :
$config['default_host'] = 'tls://mail.ourdomain.com';
$config['smtp_server'] = 'tls://mail.ourdomain.function.com';
$config['imap_conn_options'] = array(
'ssl' => array(
'verify_peer' => true,
'verify_peer_name' => true,
'peer_name' => 'mail.ourdomain.com',
'ciphers' => 'TLSv1+HIGH:!aNull:@STRENGTH',
'capath' => '/etc/ssl/certs',
'cafile' => '/etc/ssl/certs/chain.pem',
'local_cert' => '/etc/ssl/certs/combine.pem',
),
);
$config['smtp_conn_options'] = array(
'ssl' => array(
'verify_peer' => true,
'verify_peer_name' => true,
'peer_name' => 'mail.ourdomain.com',
'ciphers' => 'TLSv1+HIGH:!aNull:@STRENGTH',
'capath' => '/etc/ssl/certs',
'cafile' => '/etc/ssl/certs/chain.pem',
'local_cert' => '/etc/ssl/certs/combine.pem',
),
);
The combine.pem file contains the private key and server certificate.