How bad is lack of reverse DNS / sending email

At work we run an email server on the end of an ADSL line. (not this
one, BTW)

It's been working for years. We have been stuffing outgoing emails
into the ISP's SMTP server because we were advised that sending emails
directly from an ADSL connection (even if it is a "fixed" IP) is not
advisable because the IP comes out of the ISP's dynamic IP block and
these blocks are blacklisted.

More recently, the ISP has been doing some anti-spam measures which
have been delaying outgoing emails by anything up to an hour.

So we have changed the outgoing email to go directly via DNS.

The IP did not have reverse DNS set up.

It works, but we have noticed that emails to AOL do not arrive. Emails
to yahoo.co.uk arrive but after a while (the response on the
connection to yahoo is "delivery deferred").

So we went back to the old way.

Following our request, the ISP has now set up reverse DNS on the IP so
we will try again a couple of days from now.

The ISP claims that this IP was never on any dynamic block.

Is transmitting emails directly really a problem?

In article <(E-Mail Removed)>,
Peter <occassionally-(E-Mail Removed)> wrote:
>At work we run an email server on the end of an ADSL line. (not this
>one, BTW)
>
>It's been working for years. We have been stuffing outgoing emails
>into the ISP's SMTP server because we were advised that sending emails
>directly from an ADSL connection (even if it is a "fixed" IP) is not
>advisable because the IP comes out of the ISP's dynamic IP block and
>these blocks are blacklisted.
>
>More recently, the ISP has been doing some anti-spam measures which
>have been delaying outgoing emails by anything up to an hour.
>
>So we have changed the outgoing email to go directly via DNS.
>
>The IP did not have reverse DNS set up.
>
>It works, but we have noticed that emails to AOL do not arrive. Emails
>to yahoo.co.uk arrive but after a while (the response on the
>connection to yahoo is "delivery deferred").
>
>So we went back to the old way.
>
>Following our request, the ISP has now set up reverse DNS on the IP so
>we will try again a couple of days from now.
>
>The ISP claims that this IP was never on any dynamic block.
>
>Is transmitting emails directly really a problem?

It shouldn't be, but you might want to periodically check your IP
address in the various RBL checkers - eg:

http://www.mob.net/~ted/tools/rbl.php3
http://www.completewhois.com/rbl_lookup.htm

Can't you ask your ISP to whitelist your site?

Gordon

[Gordon Henderson], on 16 Jul 2007 14:52:45 GMT, said :-

>In article <(E-Mail Removed)>,
>Peter <occassionally-(E-Mail Removed)> wrote:

>>Is transmitting emails directly really a problem?

Yes, don't do. Get a proper mail server IP address/rDNS setup. If you
are on a dynamic IP addressing system, you will get blocked
announcements sooner or later (e.g. SORBS).

>Can't you ask your ISP to whitelist your site?
>

That won't help one bit.

Peter wrote:

> Following our request, the ISP has now set up reverse DNS on the IP so
> we will try again a couple of days from now.
>
> The ISP claims that this IP was never on any dynamic block.

You probably have a static DHCP address still within the general dynamic
block. It shouldn't be a problem - unless you sending to AOL or Yahoo/BT

> Is transmitting emails directly really a problem?

No, not really..... but

AOL are particularly draconian with their anti-spam policy and won't
allow mail from a dynamic range, in you mail server software their is
usually some way of setting exceptions so that *@aol.com can be relayed
through the ISP instead.
Yahoo/BT use a terrible anti-spam method called grey-listing, again if
you send these mails through your ISP you shouldn't get any problems.

You may want want to setup SPF for your domain
(http://www.openspf.org/Introduction) which may up your chances of
getting mail to Yahoo/AOL and other stupid ISPs that implement stupid
anti-spam measures that they are overly cagey about.

Spin Dryer wrote:
> [Gordon Henderson], on 16 Jul 2007 14:52:45 GMT, said :-
>
>> In article <(E-Mail Removed)>,
>> Peter <occassionally-(E-Mail Removed)> wrote:
>
>>> Is transmitting emails directly really a problem?
>
> Yes, don't do. Get a proper mail server IP address/rDNS setup. If you
> are on a dynamic IP addressing system, you will get blocked
> announcements sooner or later (e.g. SORBS).

Even when you purchase a business solution with a fixed IP with correct
rDNS, the entry can still exist in SORBS as a dynamic range and they
refuse to delist.
Which is very good reason IMHO, not to block email for that reason alone.

CheekyMonkey <(E-Mail Removed)> wrote:

>> The ISP claims that this IP was never on any dynamic block.
>
>You probably have a static DHCP address still within the general dynamic
>block. It shouldn't be a problem - unless you sending to AOL or Yahoo/BT

I asked them that specific question and their reply was that the IP
was never used for dynamic allocation.

The problem is the usual one - the 1st level support people don't
really know and the 2nd level support cannot be contacted directly.

Yahoo seemed to work despite lack of a rDNS but AOL doesn't.

occassionally-(E-Mail Removed) wrote:
> CheekyMonkey <(E-Mail Removed)> wrote:
>
>>> The ISP claims that this IP was never on any dynamic block.
>> You probably have a static DHCP address still within the general dynamic
>> block. It shouldn't be a problem - unless you sending to AOL or Yahoo/BT
>
> I asked them that specific question and their reply was that the IP
> was never used for dynamic allocation.

Did it have a generic rDNS entry before? i.e. customer132123.plus.net.
If so, people like Sorbs may have listed it.

>More recently, the ISP has been doing some anti-spam measures which
>have been delaying outgoing emails by anything up to an hour.

What are these anti-spam measures exactly?

CheekyMonkey <(E-Mail Removed)> wrote:

>>>> The ISP claims that this IP was never on any dynamic block.
>>> You probably have a static DHCP address still within the general dynamic
>>> block. It shouldn't be a problem - unless you sending to AOL or Yahoo/BT
>>
>> I asked them that specific question and their reply was that the IP
>> was never used for dynamic allocation.
>
>Did it have a generic rDNS entry before? i.e. customer132123.plus.net.
>If so, people like Sorbs may have listed it.

There was no entry. There is now though.

> >More recently, the ISP has been doing some anti-spam measures which
> >have been delaying outgoing emails by anything up to an hour.
>
>What are these anti-spam measures exactly?

I have no idea; they won't say. I *guess* they are queing up emails
and looking for spamming patterns. They say they had problems with
getting blacklisted (which is quite true).

Peter wrote:
> At work we run an email server on the end of an ADSL line. (not this
> one, BTW)
>
> It's been working for years. We have been stuffing outgoing emails
> into the ISP's SMTP server because we were advised that sending emails
> directly from an ADSL connection (even if it is a "fixed" IP) is not
> advisable because the IP comes out of the ISP's dynamic IP block and
> these blocks are blacklisted.
>
> More recently, the ISP has been doing some anti-spam measures which
> have been delaying outgoing emails by anything up to an hour.
>
> So we have changed the outgoing email to go directly via DNS.
>
> The IP did not have reverse DNS set up.
>
> It works, but we have noticed that emails to AOL do not arrive.

But they get accepted by AOL? What do your server logs say?

> Emails
> to yahoo.co.uk arrive but after a while (the response on the
> connection to yahoo is "delivery deferred").

That sounds like greylisting.

> So we went back to the old way.
>
> Following our request, the ISP has now set up reverse DNS on the IP so
> we will try again a couple of days from now.
>
> The ISP claims that this IP was never on any dynamic block.
>
> Is transmitting emails directly really a problem?

Yes, it can be a problem as the others have said. Checking blacklists
and server logs on a daily basis should help though, and if you are on a
blacklist the provider usually offers information on how to get off
their list again.

Regards,
Gunde

Gundemarie Scholz <(E-Mail Removed)> wrote

>Yes, it can be a problem as the others have said. Checking blacklists
>and server logs on a daily basis should help though, and if you are on a
>blacklist the provider usually offers information on how to get off
>their list again.

The question is: if one is transmitting one's business emails from
one's own IP (not the ISP's SMTP server) how could one get
blacklisted? That IP will never get used for spam (not an open relay
etc).