SMTP Error (-1): Connection to server failed.

[Magnus5405]

Im running Roundcube on a server and hMailServer on a virtual machine within the server which hosts roundcube. I can receive emails but i cannot send because i get error "SMTP Error (-1): Connection to server failed."

Code: [Select]

[] ERROR: Failed to connect socket: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
 ()
[]: <> SMTP Error: Connection failed: Failed to connect socket: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
 in \program\lib\Roundcube\rcube.php on line 1667 (POST /?_task=mail&_unlock=loading1535883982562&_lang=en_US&_framed=1&_action=send)
Hope you can help solve my problem

Thanks in advance!
 - Magnus H