Trust self signed certificate

If you have errors in /usr/share/webapps/owncloud/data/owncloud.log like those:

{
"reqId":"948346990c067b04429da95d8081aacd",
"remoteAddr":"192.168.122.1",
"app":"PHP",
"message":"stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages:\nerror:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed at \/usr\/share\/webapps\/owncloud\/3rdparty\/phpmailer\/phpmailer\/class.smtp.php#273",
"level":3,
"time":"2015-06-02T09:03:13+00:00"
}
{
"reqId":"948346990c067b04429da95d8081aacd",
"remoteAddr":"192.168.122.1",
"app":"mail",
"message":"SMTP Error: Could not connect to SMTP host.",
"level":3,
"time":"2015-06-02T09:03:13+00:00"
}

That may mean you have untrusted or self-signed certificate on SMTP server.
To deal with them you have to trust your certificate with these commands (example.com - your SMTP server name):

(inside container):

openssl s_client -showcerts -connect example.com:443 </dev/null 2>/dev/null |\
  openssl x509 -outform PEM >  /etc/ca-certificates/trust-source/anchors/example.com.crt
trust extract-compat

(outside container, oc - container name):

docker exec oc openssl s_client -showcerts -connect example.com:443 </dev/null 2>/dev/null |\
  openssl x509 -outform PEM >  /etc/ca-certificates/trust-source/anchors/example.com.crt
docker exec oc trust extract-compat