Comcast rejects my mail because I smarthost and spam filter

Exchange 2000

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Comcast rejects my mail because I smarthost and spam filter

Postby JN » Thu, 04 Sep 2008 09:25:28 GMT

I am kind of stuck between a rock and a hard place here.  We get a ton of 
SPAM so filter our email by having our MX records listed servers at an 
Anti-SPAM service company.  They filter the mail, then send us all the good 
mail.  Works GREAT!

Also, Verizon and a bunch of other companies last year were rejecting our 
email because it was coming from our static IPs which are not registered as 
belonging to an ISP.  Just a customer of one.  We got around this by using 
our Anti-SPAM service companies smart hosting feature and all was good.

Now those complete losers at Comcast our rejecting our emails because we are 
not sending it directly to them.  But if I turn off the smarthost settings, 
tons of other customers and vendors will reject our emails.  Is there anyway 
to configure Exchange to send all email through the smart host, except for

Re: Comcast rejects my mail because I smarthost and spam filter

Postby Lanwench [MVP - Exchange] » Thu, 04 Sep 2008 09:58:48 GMT

Who's your ISP?

There's only so much you can do about this. You can set up multiple SMTP 
connectors for various destination domains with different smarthost or "send 
directly:" settings. You can set up an SPF record. You can work with your 
ISP to get them to set up PTRs for you - and switch to another ISP who isn't 
blacklisted. But ultimately, if your recipients' mail servers are rejecting 
mail you send, all you can do is take it up with the recipient admins - and 
if they won't budge, well, you can't send mail to them. 

Re: Comcast rejects my mail because I smarthost and spam filter

Postby Michael Dragone » Thu, 04 Sep 2008 12:10:48 GMT

Just to add to Lanwench's good advice - have you contacted your antispam 
service provider? I'm sure if Comcast is rejecting mail that you smarthost 
through them then they're rejecting mail that *other* customers are 
smarthosting through them. They may be working on this problem already.

Exchange Hosted Services had a run-in with Comcast a few weeks back (delayed 
messages, etc.) which the two of them eventually resolved. If you want to 
keep doing what you're doing (smarthosting mail to the antispam provider), 
then you'll have to see if they can work things out with Comcast.

"Lanwench [MVP - Exchange]" 

Re: Comcast rejects my mail because I smarthost and spam filter

Postby John Oliver, Jr. [MVP] » Thu, 04 Sep 2008 12:19:30 GMT

To add what has been stated so far, make sure you have a valid SPF record in 
place.  Comcast was doing the same thing with a customer of mine and once I 
created an SPF Record for their domain, mail started flowing again to 
Comcast.  No issues since.

John Oliver, Jr
Exchange MVP 2008
Microsoft Certified Partner

Similar Threads:

1.550 5.7.1 Message rejected as spam by Content Filtering (state 18)

Exhchange 2007 SP2.

Users report emails being rejected from their personal services (gmail, 
yahoo, home ISPs) with the following message:
550 5.7.1 Message rejected as spam by Content Filtering (state 18)

In many cases, it is a short email containing either just a URL (as it will 
be when browsing and using the Send To function) or it is an email with a 
single line of text and a URL.

In searching on this, I see that Exchange will reject emails with "nearly" 
empty content.  

Our Exchange Content Filtering is only enabled for Rejecting messages with 
an SCL of 7.  Delete and Quarentine settings are not enabled.

How many characters are required to pass the Content Filter on Exchange?
Does a higher SCL rejection setting (8?) allow messages that are only URLs 
to be delivered?


2.Exchange Server with Comcast Smarthost?

They may not block the ports but at least here in the Seattle area the fine 
print in the agreement you have with your Comcast residential type account 
does prohibit the use of mail and other servers.

"Jared G" < XXXX@XXXXX.COM > wrote in message 
news: XXXX@XXXXX.COM ...
>I do this with a residential account. Depending on the area you are in
> Comcast doesn't always block ports 25 and 100.
> Just make sure the Outlook client is using the Exchange servers SMTP to 
> send
> out through Comcast as a smarthost. Setup the Outlook clients with an
> Exchange account if you havent already so that the defaut is to send 
> through
> the Exchange server.
> -- 
> Small Business Specialist
> Microsoft MCP
> Network+
> MS OEM Preinstallation Specialist
> "Steve" wrote:
>> Best is to host your own SMTP mail on Exchange. However, Comcast 
>> residential
>> type service doesn't allow you to run a mail or other type server so you
>> would need to switch to their more expensive business class service with 
>> a
>> static IP if available in your area. Alternatively find an ISP with DSL 
>> or
>> T1 service.
>> < XXXX@XXXXX.COM > wrote in message
>> news: XXXX@XXXXX.COM ...
>> > The Situation:
>> > I am setting up SBS 2003 with Exchange with Comcast as my ISP. (Anybody
>> > else?)
>> > I am attempting to send all email throught exchange, forwarding
>> > external email through my comcast hosted smtp.
>> >
>> > The Example:
>> > Here is an example of the information I am currently using in outlook:
>> > (This information works)
>> >
>> > Incoming Server:
>> > Outgoing Server:
>> >
>> > User1 Email:  XXXX@XXXXX.COM 
>> > User1 Username:  XXXX@XXXXX.COM 
>> > User1 Password: password1
>> >
>> > User2 Email:  XXXX@XXXXX.COM 
>> > User2 Username:  XXXX@XXXXX.COM 
>> > User2 Password: password2
>> >
>> > Using the SMTP Connector as outlined on every site regarding smarthosts
>> > or forwarding email. I enter the outgoing smtp server, along with a
>> > username and password for User1.  This allows User1 to send email
>> > internally and externally through the exchange server.  User2 however
>> > is not able to send external.  Recieving a 553 error.  This all makes
>> > sense as the authentication must match the from address.  Comcast
>> > insists that there is no method for accomplishing this, and has never
>> > heard of a smarthost.
>> >
>> > The question:
>> > How do I work around this?  I would like to keep the mail going through
>> > the ISP in the case that my internet is down, and for spam reduction,
>> > etc.  Is there an alternate ISP I should use?   Is there a program or
>> > add-on to Exchange which will allow me to specify seperate
>> > authentication details for each user?  Do I bite the bullet and host my
>> > own email?  Thanks in advance for you time and input.
>> >

3.Almost all incoming mails were rejected by content filtering

Today I find that almost all incoming mails to our Exchange 2007 edge 
transport server were rejected by content filtering. I believe the Forefront 
autoupdate or Windows updates make some changes to the Content filtering 
rule, it might have corrupted it, creating havoc. Since it just happens 
today, I don't not know if other people using Exchange 2007 and or Forefront 
are experiencing the same thing.

Is there any ideas what workaround available or wait for remedy? 

4.Connection Filtering rejects all of the mail as on the Block list

I've set up my fair share of Exchange boxes for clients of mine and
have some experience setting up Connection Filtering to use public
Blacklists. I'm running into an issue where a couple of them are
rejecting all email saying that the originator is on the Blacklist.
Both machine are SBS servers and I have gone over them to make sure
they are not set up differently than the ones I have setup and are

Here is what I have set up:

Display name: Spamhaus
DNS Suffix of Provider:
Customer Error Message to Return: The IP address %0 was rejected by
the Realtime Block List provider %2.

I have rules aslso set up for,, and 

I made sure the public IP address and A record for the mail server
forward and reverse to each other. I also made sure that the IP
addresses of both my and the problem machines are not on the any of
the blacklists (tested via

Here is the message I get back in the bouce (with some some small

Your message did not reach some or all of the intended recipients.

      Subject:	Test for Bounces
      Sent:	9/15/2007 11:34 AM

The following recipient(s) could not be reached:

      administrator@nopenadanoway on 9/15/2007 11:34 AM
            You do not have permission to send to this recipient.  For
assistance, contact your system administrator.
            < #5.7.1 smtp;550 5.7.1 $$.$$.85.2 has
been blocked by>

It doesn't seem to matter which (or all) of the Connection Filters I
have enabled, they reject the mail.

Anyone experienced this that could point me in the right direction?



5.Have exchange move spam to Junk Mail Folder instead of rejecting


I remember in the IMF settings of exchange 2003 there was the option in the 
area where you set the threshold for SCL (in 2007 the 3 options are 
quarantine to an address, reject or delete) which allowed you to set a 
threshold at which it would simply move a spam message to a users junk mail 

I have administered exchange for a long time and have had good luck with 
setting these thresholds and having a very low percentage of false 
positives...however the people here are very paranoid and want to be able to 
check each and every message the system says is spam.  So I would like to 
have exchange 07 move spam messages to thier junk mail folder however I dont 
see that as an option..?

Is there a way to do this in exchange 07?


6. **HELP**PLEASE** some of our mail being rejected as spam

7. SPAM bypassing our SPAM Filter.

8. Spam email bypassing spam filtering

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