- Plesk for Linux
Unable to receive/send e-mails.
Emails cannot be sent by using PHP script.
It is not possible to connect to the server by telnet on port 25:
# telnet <server_ip> 25
telnet: connect to address 192.0.2.2: Connection refused
Port 25 appears filtered when trying to connect from outside:
# nmap -p 25 example.com
PORT STATE SERVICE
25/tcp filtered smtp
SMTP Port 25 is blocked by a firewall.
If the firewall is configured in Plesk, open 25 port on the server in Tools & Settings > Firewall
If the firewall is not configured on the server, contact your hosting provider.
For AWS instance, open port 25 according to Amazon documentation.