Most domains send outbound mail through a relatively small number of servers. Domains should describe that set of servers in an SPF record in their DNS. Internet email receivers can then reject forged messages which don't come from an envelope sender domain's approved servers. This wizard helps domain owners identify all the servers which could be expected to send mail from their domain.

petrolprices.com's IP address is 87.124.84.111. Does that server send mail from petrolprices.com?		yes no
This wizard found 14 names for the MX servers for petrolprices.com: gy-in-f27.1e100.net, aspmx5.googlemail.com, alt1.aspmx.l.google.com, bw-in-f27.1e100.net, gx-in-f27.1e100.net, qy-in-f27.1e100.net, aspmx2.googlemail.com, iw-in-f27.1e100.net, aspmx.l.google.com, pv-in-f27.1e100.net, aspmx3.googlemail.com, aspmx4.googlemail.com, ww-in-f27.1e100.net, and alt2.aspmx.l.google.com. (A single machine may go by more than one hostname. All of them are shown.) MX servers receive mail for petrolprices.com. Do they also send mail from petrolprices.com?		yes no
Do you want to just approve any host whose name ends in petrolprices.com? (Expensive, unreliable and not recommended)		yes no
Do any other servers send mail from petrolprices.com? You can describe them by giving "arguments" to the a:, mx:, ip4:, and ptr: mechanisms. mx: takes domain names and approves all the MX servers of these domains. To keep the wizard short we left out ptr:, but it works analogously.		mail.notify-customer.com
		domain names
IP networks can be entered using CIDR notation, eg. 192.0.2.0/24		87.124.0.0/15
Could mail from petrolprices.com originate through servers belonging to some other domain? If you send mail through your ISP's servers, and the ISP has published an SPF record, name the ISP here.
Do the above lines describe all the hosts that send mail from petrolprices.com?		yes no
petrolprices.com. IN TXT "v=spf1 ip4:87.124.0.0/15 a:mail.notify-customer.com include:aspmx.googlemail.com ~all"

The SPF record:

v=spf1 ip4:87.124.0.0/15 include:aspmx.googlemail.com a:mail.notify-customer.com -all

can be explained as:

	v=spf1	This identifies the TXT record as an SPF string.
	ip4:87.124.0.0/15	Every host in the range 87.124.0.0-87.125.255.255 is allowed to send mail from petrolprices.com.
	include:aspmx.googlemail.com	Any server allowed to send mail from aspmx.googlemail.com is also allowed to send mail from petrolprices.com.
	a:mail.notify-customer.com	mail.notify-customer.com is also allowed to send mail from petrolprices.com.
	-all	No other servers are allowed to send mail from petrolprices.com. This is a good default for sites particularly concerned about forgery.

You need to transfer these records to your DNS server by yourself. No changes can be made by the wizard, it can only provide you with the data that needs to be entered into your DNS server.

petrolprices.com. IN TXT "v=spf1 ip4:87.124.0.0/15 include:aspmx.googlemail.com a:mail.notify-customer.com -all"

'petrolprices.com:v=spf1 ip4\07287.124.0.0/15 include\072aspmx.googlemail.com a\072mail.notify-customer.com -all:3600

If you run Windows DNS

Please see these instructions.

More options

If your site requires more complex configuration than this, you should read more about mechanisms. You should also review the tradeoffs involved in choosing an "all" default: see page 15 of the white paper.

You can test some pretend scenarios at one of the DNS tools. MTAs that reject mail because SPF tests failed will link to the why page.