spf-discuss
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Re: [spf-discuss] More detail on subdomains

2010-02-12 14:41:12
Okay
I'll set an SPF to tell the world not accept email from @www.edhance.com with 
www.edhance.com<http://www.edhance.com>  IN TXT "v=spf1 -all" correct?
The part that I'm not quite clear on is the part with the relay hosts. The 
relay hosts relay1.edhance.com<http://relay1.edhance.com> and 
relay0.edhance.com<http://relay0.edhance.com> don't have txt record but they 
are in the edhance.com<http://edhance.com> TXT record.  To be extra safe should 
I add a txt record for each of the relays like this: 
relay1.edhance.com<http://relay1.edhance.com>.  IN TXT "v=spf1 
ip4:67.110.143.100 -all" & relay0.edhance.com<http://relay0.edhance.com>.  IN 
TXT "v=spf1 ip4:67.110.143.99 -all"?

Thanks,
James





On Feb 12, 2010, at 3:09 PM, alan wrote:

At 19:24 12/02/2010  Friday, James R. Marcus wrote:
Yesterday I changed completely our SPF record to -all from ~all.  I started 
reading the common mistakes section of the website and wasn't completely sure 
about this part

"Publish null SPF records for your domains that don't send mail
Once you've protected your mail sending domains with SPF, if someone is trying 
to spoof you, then first thing they will try is to spoof your non-mail sending 
domains. Publishing "v=spf1 -all" says that a domain sends no mail. As an 
example, you might publish:

example.com<http://example.com>.       IN  TXT  "v=spf1 a:mail.example.com -all"
mail.example.com<http://mail.example.com>.  IN  TXT  "v=spf1 a -all"
www.example.com<http://www.example.com>.   IN  TXT  "v=spf1 -all"
"

Are there a list of common subdomains I'm supposed to add TXT records for or 
just just simple ones I can think of?

no just any that already exist in your DNS records with an A or MX record 
[there is no point creating new ones]
{any domains without an A or MX record will already be rejected by most 
mail-recievers}

but i would point out from looking at you mail to the list that your server 
actually sends with the name
relay1.edhance.com<http://relay1.edhance.com> 
(relay1.edhance.com<http://relay1.edhance.com> [67.110.143.100

so you MUST have
relay1.edhance.com<http://relay1.edhance.com>.  IN TXT "v=spf1 a -all"
or
relay1.edhance.com<http://relay1.edhance.com>.  IN TXT "v=spf1 
ip4:67.110.143.100 -all"

if you want to be kinder to us all and save us the extra lookups

if you have a second machine sending as 
mail.edhance.com<http://mail.edhance.com> the above is fine IF not you can set 
mail.edhance.com<http://mail.edhance.com> to v=spf1 -all



I have shutdown SMTP access to all but my to relay servers on the network. But 
if I don't want email to come from 
username(_at_)www(_dot_)edhance(_dot_)com<mailto:username(_at_)www(_dot_)edhance(_dot_)com>,
 do I just add this:
www.edhance.com<http://www.edhance.com> IN TXT "v=spf1 -all"

exactly {this dosn't stop mail comming from xxx(_at_)domain, it just enables 
receivers to tell it is obviously a forgery and reject it if it does, but also 
as spammer aren't so dumb it does tend to stop them trying}


thanks,
James





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:: James R. Marcus | Director, IT Operations
:: Edhance | 
jmarcus(_at_)edhance(_dot_)com<x-msg://103/jmarcus(_at_)edhance(_dot_)com>
:: v: 617-475-5360 | m: 914-772-8533
:: web: www.edhance.com<http://www.edhance.com/>




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