Basics

Have you ever received a bounce for spam that was sent by you…only it wasn’t sent by you? Email spoofing is one of the easiest concepts to understand for us, but the hardest to explain to end users who confuse spoofing with email hacking and hijacking. The way I explain it to our customers is that spoofing is simply when someone (usually spammers) sends an email that looks as if it came from one person, when it really came from someone else.

Regardless of what some email providers say, there is no honest and straight forward way to keep people from spoofing your email, unless you have access to the real sender’s mail system. However, there is a way to keep legitimate mail servers from accepting spoofed email by creating an SPF record for your domain.

An SPF record (sender policy framework) in short is a DNS record that you add to your domain’s zone file to specify which hosts are allowed to send mail on behalf of your domain. For the most part you would only want the server hosting your domain to be able to send mail, but hat most of our customers don’t realize is that they unknowingly spoof email all the time! Since ISP’s nowadays block SMTP port 25 for third-party mail servers, a lot of our customers use their ISP to send mail for their domain. This is basically how email is spoofed…you put an email address as the ‘from’ address in an email, and send it from a different mail server. Even though this is legitimate email, they are basically allowing their ISP’s mail servers to send their domain’s email, even though their ISP has no authority or management rights over that email, since the domain is hosted on another server.

We usually require our customers to generate their own SPF records so that they can specify what servers they want to be able to send mail from, that way our hands stay clean if the SPF record causes them to not be able to send email. If you go to www.openspf.org you can easily generate a custom SPF record to add to your DNS zone with little to no hassle. The questions can be a little confusing for newbies, so here’s a quick walkthrough on how to answer them.

Question 1: A-Record

linuxbabu.net's IP address is 75.126.142.72 (srv2.webhostingsuite.com).
Does that server send mail for linuxbabu.net?

The wizard will attempt to resolve the domain to an IP, then do a rDNS on the IP for a hostname. You usually want to say YES unless your mail is hosted on a different server.

Question 2: MX-Record

This wizard found 2 names for the MX servers for linuxbabu.net:

srv2.webhostingsuite.com and linuxbabu.net.
MX servers receive mail for linuxbabu.net.
Do they also send mail from linuxbabu.net?

In most cases, this will be true. Exceptions for this is if you have an irregular MX record modification, or are using another outgoing mail server or domain to send mail.

Question 3: PTR

Do you want to just approve any host whose name ends in linuxbabu.net?

Typically, you do not want to enable this setting unless you have mail accounts set up for subdomains or domains that are similar in ending that need to relay through this domain. Or, if you use a subdomain as your sending host (like mail.domain.com, etc)

Question 4: A subs

Do any other servers send mail from linuxbabu.net?

The answer is usually no. The only other server that would send on behalf of that domain would be the server name (you may need to ask your host for this), but this was already allowed in question 1. The next two fields can be left blank, unless you specifically have information to add to them.

Question 5: Include

Could mail from linuxbabu.net originate through servers belonging to some other domain?

Fill in this field mainly if you are planning on using another mail server or domain (such as your ISP, gmail, etc.) to send mail. Otherwise say no.

Question 6: ~all

Do the above lines describe all the hosts that send mail from linuxbabu.net?

Check your answers and hit yes.
At the bottom of the page you’ll see the nicely-generated SPF record that will look something like this:

"v=spf1 a mx ~all"

Adding the Zone Entry

You can add the SPF record either WHM (if you are on a cPanel server) or manually in the zone file of that domain.

The line will look something like this:

linuxbabu.net. 14400 IN TXT "v=spf1 a mx ~all"

You can then verify the addition by doing a dig on the domain:

dig linuxbabu.netTXT

# vi /etc/my.cnf

#opteron 852 4GB RAM
[mysqld]
safe-show-database
max_connections = 500
key_buffer = 150M
myisam_sort_buffer_size = 64M
join_buffer_size = 1M
read_buffer_size = 1M
sort_buffer_size = 1M
table_cache = 1024
thread_cache_size = 100
wait_timeout = 300
connect_timeout = 10
max_allowed_packet = 16M
max_connect_errors = 10
query_cache_limit = 1M
query_cache_size = 32M
query_cache_type = 1
skip-innodb
thread_concurrency=4

[mysqld_safe]
open_files_limit = 8192

[mysqldump]
quick
max_allowed_packet = 16M

[myisamchk]
key_buffer = 64M
sort_buffer = 64M
read_buffer = 16M
write_buffer = 16M[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip-locking
#skip-networking
safe-show-database
query_cache_limit=1M
query_cache_size=128M ## 32MB for every 1GB of RAM
query_cache_type=1
max_user_connections=200
max_connections=500
interactive_timeout=10
wait_timeout=20
connect_timeout=20
thread_cache_size=128
key_buffer=256M ## 64MB for every 1GB of RAM
join_buffer=1M
max_connect_errors=20
max_allowed_packet=16M
table_cache=1024
record_buffer=1M
sort_buffer_size=4M ## 1MB for every 1GB of RAM
read_buffer_size=4M ## 1MB for every 1GB of RAM
read_rnd_buffer_size=4M  ## 1MB for every 1GB of RAM
thread_concurrency=4 ## Number of CPUs x 2
myisam_sort_buffer_size=64M
server-id=1
log_slow_queries=/var/log/mysql-slow-queries.log
long_query_time=2
collation-server=latin1_general_ci
old-passwords

[mysql.server]
user=mysql
basedir=/var/lib

[safe_mysqld]
err-log=/var/log/mysqld.log
pid-file=/var/lib/mysql/mysql.pid
open_files_limit=8192

[mysqldump]
quick
max_allowed_packet=16M

[mysql]
no-auto-rehash
#safe-updates

[isamchk]
key_buffer=32M
sort_buffer=32M
read_buffer=16M
write_buffer=16M

[myisamchk]
key_buffer=32M
sort_buffer=32M
read_buffer=16M
write_buffer=16M

[mysqlhotcopy]
interactive-timeout

login into the server as root. Go to the /usr/local/src/ folder and download the latest version of vsftpd…….

# cd /usr/local/src/

# wget ftp://vsftpd.beasts.org/users/cevans…d-2.0.5.tar.gz

untar the tar.gz file.

# tar -zxvf vsftpd-2.0.5.tar.gz

Go to the directory and run the make file.

# cd vsftpd-2.0.5
# make

Once it has finished compile and execute it

# make install
# cp vsftpd.conf /etc

Now edit the config file

vi /etc/vsftpd.conf

Disable anonymous logins and enable local, at the very bottom of the file add
listen=YES

Save the file and Just start the vsftpd service and enable it in startup.

# /usr/local/sbin/vsftpd
# chkconfig vsftpd on