Sending email on HANA Cloud XS app

Hello,

I am trying to send email from HANA cloud with XS app. When SMTP server is configured to localhost:25 app works, I get messageID and queue ID but the email never gets delivered, like it stays on localhost. If I change SMTP server to our smtp server, email never gets sent. In trace I found the following:

[28022]{28022}[-1/-1] 2015-10-05 10:31:01.871238 e XsIpConnection   IPConnection.cpp(00301) : IPcon: connection to host failed!. resultCode = -10

[28022]{28022}[-1/-1] 2015-10-05 10:31:01.871342 e XSMail           SMTPConnection.cpp(00271) : Connect to host 'our.smtpserver.com:25' failed!

[28022]{28022}[-1/-1] 2015-10-05 10:31:01.871453 e JavaScript       Mail.cpp(00711) : Couldn't send mail: exception  1: no.2530005  (XSEngine/Connectivity/Smtp/SMTPConnection.cpp:272)

    error coulnd't establish connection

What else needs to be configured for HANA cloud to be able to use our SMTP server?

Best regards,

Sasha