In my opinion, there are 3 reasons for adopting SPF

1) If you have SPF records for your domain(s) and the receiving email server(s) choose to use SPF then email claiming to originate from your domain(s) is rejected.

2) Email inbound to your own server claiming to originate from your domains will be rejected.

3) Hijacked machines sending spam typically do not have spf records, so it is a way to lower the amount of spam on your servers.

This said SPF records can be used by spammers for their own domains so mostly it stops people (spammers) from using your email address as a from address (which has happened to us in the past - 1000's of rejects bounced to our servers) and reduces inbound bot spam.

Finally just because you choose to publish SPF records doesn't mean that other email servers will choose to use them (some do, some don't) It is anything but perfect but it helps (a bit)

Paul



On May 30, 2011, at 4:02 PM, Steve wrote:

> Yep I saw that, but that was odd because I put in the snscomputing email
> address and it passed!  Their mail server does not exist in this network so
> it shouldn't pass.  Wondering why some places do and some places don't have
> SPF records.. 
> 
> Maybe only the mail servers that wan't to be recognized and not allow others
> to email on their behalf will register a record? 
> 
> -----Original Message-----
> From: Neil Herber (nospam) [mailtoHIDDEN@@eton.ca] 
> Sent: Monday, May 30, 2011 3:49 PM
> To: surgemailHIDDEN@etwinsite.com
> Subject: Re: [SurgeMail List] SPF Failure.
> 
> 
> 
> On 2011-05-30 3:35 PM, Steve wrote:
>> 30 00:52:56[8975052] Failed 72.38.236.206 HIDDEN@mnsi.net>
>> HIDDEN@snscomputing.com> 768 <1306731171HIDDEN@@surgemail.wavedirect.net>
>> "[72.38.236.206] [Site snscomputing.com (72.167.238.201) before data sent:
>> 550 5.7.1 SPF unauthorized mail is prohibited.] Please see
> 
> If you look at:
> http://www.mxtoolbox.com/SuperTool.aspx?action=spf%3amnsi.net
> 
> it will show you the only IPs authorized to send mail from mnsi.net. If
> the IP of your server (which seems to be 72.167.238.201) is not in that
> list (they are all 216.8.x.x IPs), the SPF will fail.
> 
> -- 
> Neil Herber
> 
> 
>