It is not possible to connect to port 587 on Windows server with MailEnable.
However, MailEnable is configured properly:
Mailenable SMTP settings:
SMTP -> Properties -> "Inbound" tab -> "Port Settings" Settings
SMTP port = 25
Submission port = 587
This issue is likely caused by an incorrect firewall configuration - port 587 is filtered.
Open "Windows Firewall with Advanced Security" on the server and create a new rule:
Accept all inbound connections on port 587.
The following steps are required to open a custom port:
1. Open the start menu
2. Type firewall
3. Open Windows Firewall with Advanced Security
4. Open Inbound Rules
5. New Rule...
6. Choose Port type
7. Choose TCP, and enter the required port - in our case, 587
8. Choose to Allow the connection
9. Choose all three profiles (Domain+Private+Public)
10. Enter a custom rule name, e.g. "Port 587"
11. Press finish.
Make sure that you can connect with telnet. For example:
# telnet 184.108.40.206 587
Connected to 220.127.116.11.
Escape character is '^]'.
220 domain.tld ESMTP MailEnable Service, Version: 6.5-- ready at 05/06/14 20:38:39
You could also see knowledgebase article #213932745 to check the other ports used by Parallels Plesk Panel.