SMTP does not work on port 587 in MailEnable on Plesk

Symptoms

• It is not possible to connect to port 587 on Plesk Windows server with MailEnable

• Connecting to port 587 on the server with telnet is not possible:

  # telnet 192.0.2.2 587
  Trying 192.0.2.2…
  telnet: connect to address 192.0.2.2: Connection refused

• Port 587 appears filtered when trying to connect from outside:

  # nmap -p587 192.0.2.2
  …
  PORT STATE SERVICE
  587/tcp filtered submission
  Nmap done: 1 IP address (1 host up) scanned in 0.59 seconds

• MailEnable is configured as described in this article:
  

Cause

Port 587 is filtered in a firewall or by Internet Service Provider.

Resolution

Make sure that inbound connection to port 587 is allowed in Plesk Firewall as explained in The Plesk Firewall ( Windows): Viewing and Managing Allowed Inbound Connections:

1. Log into Plesk
2. Go to Tools & Settings > Firewall > Firewall Rules > Add Firewall Rule
3. Specify the firewall rule for port 587 and apply the changes

Note: In case Internet Service Provider blocked the port, contact their support in order to open it from their side.