[Mimedefang] Cross-Post about SA Rule RCVD_IN_DYNABLOCK returning false positives

Nels Lindquist nlindq at maei.ca
Fri Oct 3 14:21:02 EDT 2003


This is starting to become off-topic for MIMEDefang, but it's still 
slightly relevant because if the potential to use MD to avoid calling 
SA on your client's mail.

On 3 Oct 2003 at 9:56, VonEssen, John wrote:

> I secure relaying by implementing a POP before SMTP secheme. IP's of
> all successful POP3 logins for the last 30 minutes are put into a
> sendmail map. SMTP relaying is only allowed for those IP's 

Is there any way to get that information into MIMEDefang so you can 
avoid calling SpamAssassin on customer mail?
 
> I disagree with you regarding my case being unique. What about people
> who purchase their own domain and go with hostway or valueweb. To use
> @theirdomain.com email, hostway or valueweb gives them access to use
> their non-ISP mail server.

I don't know the technical details for a given ISP, but generally 
when you buy access which allows a server to be used, you get a 
static IP address.  No dynamic IP, no Dynablock list.

> When I was at Penn State, all mail was done via POP3/SMTP/ SO you would
> connect however, local ISP, DSL, etc.,. and then just configure Outlook
> or Netscape to use your desired mail server. 

Which is very different from having your mail client connect directly 
to the MX for every individual recipient address.  That *is* the case 
for lots of spammers' ratware which tends to be run from a temporary 
disposable dynamic account.

> I don't understand why NOT using your ISP's mail server is such a big
> deal. Its easy to allow remote and secure relaying. People have been
> doing it for years.

We're not talking about relaying.  When one of your clients sends 
mail to me, they're relaying through *you*--their mail client will 
not connect directly to my mail server.  Hence, the DYNABLOCK test 
will not trigger for such mail, because *your* mail server isn't on 
the list, and that test is only run for the relay connecting to my 
server.

> Its like your punishing the client because they use a third party mail
> server. Most clients do this because the ISP mail servers suck - No
> virus or spam filtering - or if they do have it the quality is poor. 

Why should one care about virus/spam filtering on the *outgoing* 
relay?  Is there any compelling reason why your clients need to use 
your SMTP server in the first place?  If all they want is to receive 
filtered mail, they can easily use your server as their POP3/IMAP 
server while retaining their ISP's mail relay for outgoing mail.

----
Nels Lindquist <*>
Information Systems Manager
Morningstar Air Express Inc.




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