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comcast SPF record

 

 

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tnelson at starpoint

Jun 15, 2004, 7:28 AM

Post #1 of 3 (2033 views)
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comcast SPF record

I have setup SPF for our domain (starpoint.com) and think it's working properly
and well.

I have seen mentions on this thread of comcast.net setting up SPF records as
well, which I'm very interested in as now we are blocking all incoming comcast
e-mail which is making some of my users quite unhappy.

I have tried to check for SPF records for comcast.net and don't see any:

tnelson [at] njmai:~$ host -t mx comcast.net
comcast.net mail is handled by 5 gateway-s.comcast.net.
comcast.net mail is handled by 5 gateway-r.comcast.net.
tnelson [at] njmai:~$ host -t txt comcast.net
tnelson [at] njmai:~$ host -t txt verizon.net
verizon.net text "v=spf1 ip4:206.46.170.0/24 ip4:206.46.128.33
ip4:206.46.128.101 ip4:209.84.13.21 ip4:209.84.13.20 ?all"


Amy I missing something or has comcast.net not setup it's SPF records yet?

Thanks,
Tony

--
Tony Nelson
Director of IT Operations
Starpoint Solutions LLC
115 Broadway, 2nd Fl
New York, NY 10006



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spf at kitterman

Jun 15, 2004, 7:38 AM

Post #2 of 3 (1919 views)
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RE: comcast SPF record [In reply to]

> -----Original Message-----
> From: owner-spf-help [at] v2
> [mailto:owner-spf-help [at] v2]On Behalf Of Tony Nelson
> Sent: Tuesday, June 15, 2004 10:28 AM
> To: spf-help [at] v2
> Cc: jaleles [at] starpoint
> Subject: [spf-help] comcast SPF record
>
>
> I have setup SPF for our domain (starpoint.com) and think it's
> working properly
> and well.
>
> I have seen mentions on this thread of comcast.net setting up SPF
> records as
> well, which I'm very interested in as now we are blocking all
> incoming comcast
> e-mail which is making some of my users quite unhappy.
>
> I have tried to check for SPF records for comcast.net and don't see any:
>
> tnelson [at] njmai:~$ host -t mx comcast.net
> comcast.net mail is handled by 5 gateway-s.comcast.net.
> comcast.net mail is handled by 5 gateway-r.comcast.net.
> tnelson [at] njmai:~$ host -t txt comcast.net
> tnelson [at] njmai:~$ host -t txt verizon.net
> verizon.net text "v=spf1 ip4:206.46.170.0/24 ip4:206.46.128.33
> ip4:206.46.128.101 ip4:209.84.13.21 ip4:209.84.13.20 ?all"
>
>
> Amy I missing something or has comcast.net not setup it's SPF records yet?
>
> Thanks,
> Tony
>
AFAIK Comcast has not set up an SPF record. I have asked. What I have done
in the meantime is guess at the IP range that Comcast uses for their SMTP
servers and added that to my SPF record.

Here's what I've come up with (sent myself a number of e-mails):

sccrmhc12.comcast.net (204.127.202.56)
sccrmhc11.comcast.net (204.127.202.55)
sccrmhc13.comcast.net (204.127.202.64)

Note that I am part of the Maryland Comcast network, so other segments of
their network probably use different SMTP servers. Since I only seem to be
hitting servers 11-13, I assume people in other parts of the network use
different servers that may or may not be part of the same IP block. Based
on what I found, I've got ip4:204.127.202.0/24 in my SPF record.

Until Comcast can be convinced to publish the SPF record, this is the best I
can do. For anyone else reading this, I wouldn't rely on my results
however. YMMV. I'd be interested to hear what anyone else came up with.

Are you saying that you are blocking based on lack of SPF? If you are, I
think it's very premature to do that.


Scott K

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tnelson at starpoint

Jun 15, 2004, 7:47 AM

Post #3 of 3 (1946 views)
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RE: comcast SPF record [In reply to]

Quoting spf [at] kitterman:

[snip]

> Are you saying that you are blocking based on lack of SPF? If you are, I
> think it's very premature to do that.
>

Oh not at all. I use spfilter to download various RBL lists to block on.
Currently I am downloading SPAM_SAFE and COUNTRY_SAFE and generate an access.db
for my sendmail server. It actually works quite well w/ the various KOREA,
CHINA, etc..

Thanks for your detailed reply.

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