- Plesk for Linux
- Plesk for Windows
- Trying configuring Gmail feature "Send mail as" and specifying Plesk mail server as SMTP server (mail.example.com) the following error is shown:
CONFIG_TEXT: Couldn't reach server. Please double-check the server and port number.
- The same works fine if IPv4 address is specified instead of mail.example.com.
- Domain resolves both to IPv4 and IPv6:
# dig +short example.com A
# dig +short example.com AAAA
- 25 port through IPv6 is filtered:
# nmap -6 -p25 2001:db8:f61:a1ff:0:0:0:80
PORT STATE SERVICE
25/tcp filtered smtp
It is not possible to establish telnet connection to 25 port via IPv6:
# telnet 2001:db8:f61:a1ff:0:0:0:80 25
telnet: connect to address 2001:db8:f61:a1ff:0:0:0:80: Connection timed out
Google uses IPv6 as a priority to connect to the mail server, as a result, the connection fails.
Open the connection to the 25th port through IPv6 in a firewall or just use the IPv4 address as SMTP server.