Hello Atanet,
I would suggest one way see where. you can use the telnet command to find whether the domain's mail service is running on 25 or not, you will have to run the telnet command in the command prompt;
Example: telnet domain.com 25
If you see the output
> 'Trying 11.11.11.111... Your domain is not using the 25 port.
Or, if you see the output like this:
telnet domain.com 25
Trying 11.11.11.111...
Connected to domain.com.
Escape character is '^]'.
Also, the command will show the IP address of on which your domain is running not: 11.11.11.111...