Unable to send mail via SMTP

We have an issue with sending email from our server. We used to sent successful with Gmail configuration but failed on our company. We tried with multiple parameters enabled or disabled (TLS, Anonymous users, port 587 and 25, SSL disabled on Sitefinity, specify domain or not on Sitefinity, etc…), and it always result in Remote(SocketError) on our logs.
We have multiple other applications configured the exact same way (SharePoint, monitoring …) and they all work perfectly with the same method (basic SMTP on port 25). These info below used to configure. Do we need to check on anythings else or lack of any informations? Thanks. 
 
Host: mail.comp.com 
Port: 25 

Username: our company email
Domain: blank
DeliveryMethod: Network
EnableSSL: true
Timeout: 10000
PickupDirectoryLocation: blank
DefaultSenderEmailAddress: blank