I’m trying to build a mail server, but when I tried to check the if TCP Port 25 (outbound) is blocked
I got the following
[email protected]:~# telnet gmail-smtp-in.l.google .com 25
Connected to gmail-smtp-in.l.google .com.
Escape character is ‘^]’.
421 service not available (connection to blacklisted host (18.104.22.168 - DNSBL))
Connection closed by foreign host.
When I googled it, I found that DNSBL Stands For Domain Name System Blacklist
I checked port 25 For My Public IP Address
And found it’s opened, I also checked the following websites to see if my Public IP Address is blacklisted
But found that My Public IP Address is not blacklisted
I also did telnet from another server in another location and it could connect successfully
Now what should I do ?