I recently migrated from Fedora to CentOs and forgot to configure
SMART_HOST in sendmail.mc. I discovered this after my ISP cut off
my internet access because they say I was sending spam. Would the
lack of a SMART_HOST make ordinary mail look like spam to an ISP?
How come outgoing e-mail worked at all?

On Aug 20, 1:46*pm, Bob Tennent <B...@cs.queensu.ca> wrote:

> I recently migrated from Fedora to CentOs and forgot to configure
> SMART_HOST in sendmail.mc. *I discovered this after my ISP cut off
> my internet access because they say I was sending spam. *Would the
> lack of a SMART_HOST make ordinary mail look like spam to an ISP?
> How come outgoing e-mail worked at all?

Are you sure they said you were sending spam? If so, ask them for a
copy of the spam so you can investigate.

Most likely, what they were really complaining about was that you were
running a mail server and you weren't supposed to be.

Outgoing e-mail worked because you delivered it, which you're not
supposed to do unless you're running a mail server.

DS

On 2008-08-20, Bob Tennent <BobT@cs.queensu.ca> wrote:
>
>
> I recently migrated from Fedora to CentOs and forgot to configure
> SMART_HOST in sendmail.mc. I discovered this after my ISP cut off
> my internet access because they say I was sending spam. Would the
> lack of a SMART_HOST make ordinary mail look like spam to an ISP?
> How come outgoing e-mail worked at all?

With a smart host, all your outgoing mail is sent through your ISP's
mail server. Without it, your computer sends mail directly to port 25
of the destination address. Unfortunately, if your PC doesn't have
a registered domain name that matches the "From" address in your email,
or if your IP address is in a block of addresses used for residential
subscribers, your email looks like spam. Also, if your sendmail wasn't
configured properly, it's possible your system could have been an open
relay for actual spam.

On Aug 20, 3:03*pm, Bill Marcum <marcumb...@bellsouth.net> wrote:

> ... Unfortunately, if your PC doesn't have
> a registered domain name that matches the "From" address in your email,
> ... your email looks like spam.

The rest of your comments were dead on, but this is nonsense. This
would imply that each domain that can be used in a 'From' address must
have its own mail server, which is completely untrue. Many mail
servers handle mail from dozens of domains.

I suppose you could also mean that the mail server that sends outbound
email from a particular domain must (or at least should) have some
relationship to the MX servers listed to handle inbound email to that
domain. That is also untrue.

You could almost have meant something accurate if this was some kind
of reference to SPF. But that has nothing to do with a registered
domain name matching a from address.

DS

On Wed, 20 Aug 2008 14:46:35 -0700 (PDT), David Schwartz wrote:
> On Aug 20, 1:46*pm, Bob Tennent <B...@cs.queensu.ca> wrote:
>
>> I recently migrated from Fedora to CentOs and forgot to configure
>> SMART_HOST in sendmail.mc. *I discovered this after my ISP cut off
>> my internet access because they say I was sending spam. *Would the
>> lack of a SMART_HOST make ordinary mail look like spam to an ISP?
>> How come outgoing e-mail worked at all?
>
> Are you sure they said you were sending spam? If so, ask them for a
> copy of the spam so you can investigate.

I finally got around to reading mail to root and I now see what
happened: the outgoing mail was mostly rejected by the destination sites
and returned, no doubt with a nasty complaint to the ISP. Mea culpa.

Bob T.

On Wed, 20 Aug 2008 16:59:11 -0700 (PDT), David Schwartz wrote:
> On Aug 20, 3:03*pm, Bill Marcum <marcumb...@bellsouth.net> wrote:
>
>> ... Unfortunately, if your PC doesn't have
>> a registered domain name that matches the "From" address in your email,
>> ... your email looks like spam.
>
> The rest of your comments were dead on, but this is nonsense. This
> would imply that each domain that can be used in a 'From' address must
> have its own mail server, which is completely untrue. Many mail
> servers handle mail from dozens of domains.

I think he meant working reverse DNS.

--
* John Oliver http://www.john-oliver.net/ *

On Aug 21, 11:13*am, John Oliver <joli...@john-oliver.net> wrote:
> On Wed, 20 Aug 2008 16:59:11 -0700 (PDT), David Schwartz wrote:
> > On Aug 20, 3:03*pm, Bill Marcum <marcumb...@bellsouth.net> wrote:

> >> ... Unfortunately, if your PC doesn't have
> >> a registered domain name that matches the "From" address in your email,
> >> ... your email looks like spam.

> > The rest of your comments were dead on, but this is nonsense. This
> > would imply that each domain that can be used in a 'From' address must
> > have its own mail server, which is completely untrue. Many mail
> > servers handle mail from dozens of domains.

> I think he meant working reverse DNS.

Possibly, but that wouldn't involve anything matching the "From"
address.

DS

On 2008-08-20, Bob Tennent <BobT@cs.queensu.ca> wrote:

> I recently migrated from Fedora to CentOs and forgot to configure
> SMART_HOST in sendmail.mc. I discovered this after my ISP cut off
> my internet access because they say I was sending spam. Would the
> lack of a SMART_HOST make ordinary mail look like spam to an ISP?

Many ISPs automatically flag inbound mail arriving directly from dynamic
IP addresses as spam.

> How come outgoing e-mail worked at all?

Your ISP doesn't block outbound port 25 from dynamic IP addresses.

--

John (john@os2.dhs.org)
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