Sendmail on a LAN

Tim ignored_mailbox at
Wed Aug 18 13:13:54 UTC 2010

>> Are you aware that if your SMTP server is on an IP in the range of
>> addresses your ISP doles out to its private customers, you may be on a
>> blacklist of IPs to ignore.  It's a common practice for many other mail
>> servers, or their incoming mail filters, to only accept mail sent from
>> ISP mail servers, and other large networks.

Ed Greshko:
> I believe you are speaking of RBL services such as  Yes,
> indeed they try to keep a list of IP address ranges that are used by
> ISP's to be dynamically allocated.  And, indeed there can be problems
> when the list they keep doesn't match with reality.  In the case of
> "good" RBL services like spamhaus they will fix the issue quickly with
> the proper evidence that the IP in question really isn't allocated
> dynamically.

The trouble is that the problem is external, and out of your control.
Others can use any number of filtering techniques, good or bad.  If your
on just one black list, that's a problem.

You can also strike the other blacklisting issue.  e.g. One of my former
ISPs, Optus, was on many blacklists for doing sweet Fanny Adams about
spam coming through their systems.  Any IP associated with them was
tarred with that brush, and your mail could get rejected, no matter how
you tried sending (your own SMTP server, their SMTP server...).  To make
matters worse, they're one of the big ISPs and telcos in this country,
and the backbone for many smaller ISPs.  That situation went on for
years and years.  Long after I left them they were still in that boat,
and I've given up checking to see if it is still the case.

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