Testing cPanel mail server on MXtoolbox

Using a cPanel server? Getting “Timeout waiting for response after 15 seconds” error or exclamation mark on some SMTP tests on MXtoolbox?

SMTP test failed!It’s quite easy to fix. First of all, you have to login to WHM and to Exim Configuration Manager. Find the “Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam” option and set it to “off”.

Now, your SMTP test should look something like this:

SMTP test successful!


DDOS/SYN flood prevention settings in CSF

How to prevent DOS Attack using CSF firewall?

CSF is iptables based firewall. It’s one of the most effective and is commonly used on Linux servers.

You can try eliminating DDOS attack to Apache using the following steps:

1. vim /etc/csf/csf.conf
2. CT_LIMIT= "60"

Here 60 is the max number connections from an IP to your server.

3. CT_PORTS = "80"

This option is used to specify the port for which you want prevent DDOS attack. Since our aim is to prevent the DDOS attack to Apache – port 80.

If you’ve done the steps above, CSF firewall will block all IPs that have 60 connections established to port 80 on your server.

Please note: In CT_PORTS you can specify the ports to be prevented for DDOS attack, like SMTP and POP3. It’s also possible to specify any number of ports in a comma separated format, like CT_PORTS=”80,25,110″

Continue reading DDOS/SYN flood prevention settings in CSF

cPanel + CloudFlare issue (CSS being messed up)

The problem seems to be occurring for all accounts accessed through domain name:
But not when logging into cPanel through the server’s hostname at https://server.example.com/cpanel instead.
This appears to be caused by “domain.com” using CloudFlare’s IP address for its A record and conflicting with the “Cookie IP validation”.
You should do the following:
WHM > Tweak Settings

Cookie IP validation > disabled
If you’d like to continue using “Cookie IP validation” on your server, users will need to access cPanel through the server’s IP or hostname directly to circumvent this issue.

How to troubleshoot spam issues with Exim

Check amount of mail in queue

# exim -bpc

As you can see, we have a pretty decent amount of mail in our Exim queue.

Now, let’s list all messages in the queue and pick a random message ID to check its’ header.

 # exim -bp
 4d       1cuyBm-0000Cu-3h <root@server.example.com>
 208P Received: from $user by server.example.com with local (Exim 4.82)
(envelope-from <$user@server.example.com>
id 1cuyBm-0000Cu-3h
for test@server.com Sat, 21 Mar 2015 21:03:06 -0400
027T To: mail@server.com
019 Subject: Hello!
091 X-PHP-Script: domain.com/uploads/page.php for "$IPADDRESS"
023 X-Priority: 3 (Normal)

Continue reading How to troubleshoot spam issues with Exim