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Got Blacklisted By DNSBL Or Gmail

Hi Everyone

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
Trying 74.125.71.27…
Connected to gmail-smtp-in.l.google .com.
Escape character is ‘^]’.
421 service not available (connection to blacklisted host (74.125.71.27 - 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 www.yougetsignal.com/tools/open-ports

And found it’s opened, I also checked the following websites to see if my Public IP Address is blacklisted

mxtoolbox.com/blacklists.aspx

www.dnsbl.manitu .net/

check.spamhaus.org

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 ?

Port 25 (outbound) is open, which means your mail server can establish SMTP connection on port 25 to the recipient’s SMTP server.

However, if your IP address is blacklisted, your email will be refused.

That’s two different situations.

There are two kinds of blacklists:

  • Internal blacklist
  • Public blacklist

mxtoolbox can only show you the public blacklists like spamhaus. Gmail and Outlook have internal blacklists. Mxtoolbox can’t show you the Gmail and Outlook blacklists.

If your IP address is blacklisted by Gmail, you need to change your server IP address or set up SMTP relay.

FYI, I run my mail server on ScalaHosting, which isn’t backlisted by Gmail.

1 Like

Thank You so much @LinuxBabe
I really appreciate your help

Thanks for your advice about setting up SMTP Relay & Your Recommendation regarding ScalaHosting, definitely I’ll purchase a VPS using your links

Just Another Add Info, When I tried to send email to my gmail account, I found that In the logs

[email protected]:~# journalctl -f [email protected]

Jun 07 06:49:44 mail.example.com postfix/smtp[4510]: AF3EE62218: lost connection with
gmail-smtp-in.l.google.com[64.233.167.26] while receiving the initial server greeting

Jun 07 06:49:47 mail.example.com postfix/smtp[4510]: AF3EE62218: host alt1.gmail-smtp-i
n.l.google.com[142.251.9.27] refused to talk to me: 421 service not available (connection to
blacklisted host (142.251.9.27 - DNSBL))

Jun 07 06:53:47 mail.example.com postfix/smtp[4510]: AF3EE62218: lost connection with
alt3.gmail-smtp-in.l.google.com[74.125.200.26] while receiving the initial server greeting

Jun 07 06:55:47 mail.example.com postfix/smtp[4510]: AF3EE62218: to=[email protected], relay=alt4.gmail-smtp-in.l.google.com[142.250.157.26]:25, delay=729, delays=245/0.04/484/0, dsn=4.4.2, status=deferred (lost connection with alt4.gmail-smtp-in.l.google.com[142.250.157.26] while receiving the initial server greeting)

Another Added Info : I’ve Tried to connect to non-google mail server, And Tried to send to Outlook account,but got the following in the logs

Jun 07 10:31:36 mail.example.com postfix/smtp[4856]: 68CC96225A: host outlook-com.olc.protection.outlook.com[104.47.18.161] refused to talk to me: 421 service not available (connection to blacklisted host (104.47.18.161 - DNSBL))

Jun 07 10:31:38 mail.example.com postfix/smtp[4856]: 68CC96225A:
to=[email protected],
relay=outlook-com.olc.protection.outlook.com[104.47.18.225]:25,
delay=1.9, delays=0.02/0.02/0.96/0.85, dsn=5.7.1, status=bounced (host
outlook-com.olc.protection.outlook.com[104.47.18.225] said: 554 5.7.1
Message refused by DNSBL check. bl.nsZones.com / 196.202.myip.myip
This email from IP 196.202.myip.myip has been rejected. The email
message was detected as spam. (in reply to end of DATA command))

This means your IP address has been blacklisted by Outlook.

1 Like