Sending e-mail from random IP

[hape]

[EXIM] Sending e-mails from random IP

Description: sometimes we have a server with a few IP addresses and we want to send e-mails not from one IP. So we will configure exim for sending e-mails randomly from IP range with different PTRs and helo for every IP.
Assumptions:

• exim
• more than one public IP address
• may not work with IPv4 and IPv6 together

For this article we will use this subnet and revdns as examples:
Remamber to set valid PTR(revdns) and A records for IP.
[table="width: 500"]
[tr]
[td]IPv4[/td]
[td]RevDSN/Helo[/td]
[/tr]
[tr]
[td]127.10.0.1[/td]
[td]ip1.example.net[/td]
[/tr]
[tr]
[td]127.10.0.2[/td]
[td]ip2.example.net[/td]
[/tr]
[tr]
[td]127.10.0.3[/td]
[td]ip3.example.net[/td]
[/tr]
[tr]
[td]127.10.0.4[/td]
[td]ip4.example.net[/td]
[/tr]
[/table]

How to:

1. Login to server on a console as root or user with sudo access
2. Create file with helo mapping to IP: /etc/exim.helo.conf with:
   

   127.10.0.1:ip1.example.net
   127.10.0.2:ip2.example.net
   127.10.0.3:ip3.example.net
   127.10.0.4:ip4.example.net

3. Open /etc/exim.conf and find:
   

   remote_smtp:
   driver = smtp

   add below:
   

   .include_if_exists /etc/exim.ip.conf

4. Create file /etc/exim.ip.conf with:
   

   interface = "${perl{randinet}}"
   helo_data =  ${lookup{$sending_ip_address}lsearch*{/etc/exim.helo.conf}{$value} {$primary_hostname}}

5. Edit file /etc/exim.pl, and add below existing content:
   

   # Random ip selection
   sub randinet {
     @inet = ("127.10.0.1","127.10.0.2","127.10.0.3","127.10.0.4");
     return $inet[int rand($#inet+1)];
   
   }

6. Create file /usr/local/directadmin/data/templates/custom/dns_txt.conf with:
   

   |DOMAIN|.="v=spf1 a mx ip4:127.10.0.1 ip4:127.10.0.2 ip4:127.10.0.3 ip4:127.10.0.4 -all"

   You can also use ~all insted off -all - it depends on your needs, for more use Google.
7. Restart exim:
   

   service exim restart

8. Check you have no errors. That's all.
   

We use it in our company and it works for many IP addresses. Some configs aren't mine, but I think that they aren't copyrighted

FAQ

1. How to modify existing SPF records?
   It's not possible to use DirectAdmin task system to rewrite bind/named zones, so you can use this script to perform that operation:
   

   #!/bin/bash
   OLD="v=spf1 a mx ip4:YOUR_OLD_IP ~all"
   NEW="v=spf1 a mx ip4:127.10.0.1 ip4:127.10.0.2 ip4:127.10.0.3 ip4:127.10.0.4 -all"
   DPATH="/var/named/*.db"
   BPATH="/root/backup_DNS"
   TFILE="/tmp/out.tmp.$$"
   [ ! -d $BPATH ] && mkdir -p $BPATH || :
   for f in $DPATH
   do
     if [ -f $f -a -r $f ]; then
       /bin/cp -f $f $BPATH
      sed "s/$OLD/$NEW/g" "$f" > $TFILE && mv $TFILE "$f"
     else
      echo "Error: Cannot read $f"
     fi
   done

   and restart named
   

   service named restart

All operations has been performed on Centos 6.
Remember to make backups and change IPs from 127.10.0.x to your own. And sorry for my English.

 

[ozgurerdogan]

thank you. a client sends many mails (not spam mails) to hotmail and hotmail blocks ips. could this be a workaround?