Changing Exim’s Sending IP

Anyone running a shared hosting server is probably now accustomed to dealing with constant complaints about blacklisting. It’s exim’s default setup on a cPanel server to use the shared IP of the server to send email, which means that all your clients on one server are sending out email on the same IP.  All it takes is for one spammer to send out a mailing list or one customer to get hacked and run a Darkmailer script, and suddenly everyone on your server seems to be complaining about getting their mail bounced.

You can change the server’s IP address for sending email. Assuming you already have an IP set up on your server with a valid PTR, you probably already saw on the cPanel forums or some other location that you can simply change the interface lines in your /etc/exim.conf file and restart exim:

remote_smtp:
driver = smtp
interface = ${if exists {/etc/mailips}{${lookup{$sender_address_domain}lsearch*{/etc/mailips}{$value}{}}}{}}
helo_data = ${if exists {/etc/mailhelo}{${lookup{$sender_address_domain}lsearch*{/etc/mailhelo}{$value}{$primary_hostname}}}{$primary_hostname}}

dk_remote_smtp:
driver = smtp
interface = ${if exists {/etc/mailips}{${lookup{$sender_address_domain}lsearch*{/etc/mailips}{$value}{}}}{}}
helo_data = ${if exists {/etc/mailhelo}{${lookup{$sender_address_domain}lsearch*{/etc/mailhelo}{$value}{$primary_hostname}}}{$primary_hostname}}
dk_private_key = "/var/cpanel/domain_keys/private/${dk_domain}"
dk_canon = nofws
dk_selector = default

In the above example, all you’d do is comment out the interface lines and replace them with:

interface = xx.xx.xx.xx

However, this tends to be a band-aid fix, as a cPanel update or any change made in WHM’s Exim Configuration Editor will regenerate the Exim config and overwrite your change. To make this more permanent, you’ll want to use the /etc/mailips file.

To set this up initially, go into WHM > Exim Configuration and enable this option:

** Send outgoing mail from the ip that matches the domain name in /etc/mailips (*: IP can be added to the file to change the main outgoing interface) [?]

Or, in /etc/exim.conf.localopts, add/change this line:

per_domain_mailips=1

Then run

/scripts/buildeximconf
service exim restart

*The /etc/mailips file should be root:exim, chmod 440  if it doesn’t already exist.

chattr +i /etc/mailips

Now for actually changing the IP:

Changing the IP Globally

If you want everyone on the server to send out on the same IP, just add the following to /etc/mailips:

*: xxx.xxx.xxx.xxx

Then add the IP and it’s matching PTR to /etc/mail_reverse_dns:

xxx.xxx.xxx.xxx hostname.tld

This will tell Exim to use that IP for any sender on the server.

Changing the IP Per Domain

If you want your users with dedicated IP addresses to be able to use those IPs to send email as well, you can add them to /etc/mailips. cPanel actually now has documentation on how to do this properly:

http://docs.cpanel.net/twiki/bin/view/AllDocumentation/WHMDocs/EximDifferentIps

If you have multiple dedicated IP domains already, I’ve devised a simple loop you can use to populate /etc/mailips automatically:

while read line ; do DOMAIN=`echo -e $line |awk '{print $2}'` && IP=`echo -e $line |awk '{print $1}' |cut -d: -f1` && echo "$DOMAIN: $IP" >> /etc/mailips ;done < /etc/domainips

You’ll always want the wildcard line to be in there to account for any domain not listed in the file, whether it is the main server’s IP or another that you have assigned for email:

*: xxx.xxx.xxx.xxx

Then:

cp /etc/domainips /etc/mail_reverse_dns

This will set all the existing sites on dedicated IPs to send out mail on those IPs.

Deny visitors by IP address

The visitor blocking facilities offered by the Apache Web Server enable us to deny access to specific visitors, or allow access to specific visitors. This is extremely useful for blocking unwanted visitors, or to only allow the web site owner access to certain sections of the web site, such as an administration area. To set-up visitors restrictions and blocking, create a .htaccess file following the main instructions and guidance which includes the following text:

order allow,deny deny from 255.0.0.0 deny from 123.45.6. allow from all

The above lines tell the Apache Web Server to block visitors from the IP address '255.0.0.0' and '123.45.6.', note the second IP address is missing the fourth set of digits, this means any IP address which matches the firth three set of digits will be blocked, e.g. '123.45.6.10' and '123.45.6.255' would be blocked.

To set-up blocking of all visitors except yourself, create a .htaccess file following the main instructions and guidance which includes the following text:

order allow,deny allow from 255.0.0.0 deny from all

The above lines tell the Apache Web Server to block all visitors except those with the IP address '255.0.0.0', which you should replace with your own IP address.

You may add any number of 'deny from' and 'allow from' records after the 'order allow,deny'. Note the change from 'allow from all' to 'deny from all' on the bottom line, this is important and must be changed depending on your requirements. If you want to allow your visitor access, you would use 'allow from all' and place 'deny from' lines above.

Blocked visitors will be shown a '403 Forbidden' error message. You can customise this error message by following the 'Error Documents' section of this article.