[Mailman-Users] Big headers

So far, I've dealt with this entirely by getting my server whitelisted
with the ISPs that are doing that. I believe that there is a setting for
the number sent in a batch, but to go from 500 (default, I think) to 1
would be an excruciating hit to your performance. I believe all of the
discussion-list type servers (Mailman, listserv, Mercury, Majordomo, et
al) use the same mechanism, so the ISPs that are using this technique
for stopping spam will have to address legitimate list servers.

Van

Flavio wrote:

See the FAQ.

The sweet spot is typically in the range of 5 - 10.
Sadly, nope.

SMTP is an unreliable transport. ISPs have no especial obligation to
deliver received mail to their addressed users (no matter that those
users and we may feel differently). Further, the ISPs won't reveal the
filter controls they are using as they don't want the SPAMmers working
they're way around them (they also change them regularly as the SPAMmers
empirically deduce the values).

This is not accurate. SMTP is a reliable transport. It either deliveres
the message or deliveres an NDR.
When the receiver-SMTP accepts a piece of mail (by sending a "250
OK" message in response to DATA), it is accepting responsibility
for delivering or relaying the message. It must take this
responsibility seriously. It MUST NOT lose the message for
frivolous reasons, such as because the host later crashes or
because of a predictable resource shortage.

If there is a delivery failure after acceptance of a message, the
receiver-SMTP MUST formulate and mail a notification message.

MTAs which don't accept this level of reliability aren't SMTP
transports. Ones which bit bucket mail which has too many
recipients are also not SMTP compliant.

alex

This is an MTA issue. Mailman just sends the message to your MTA,
your MTA is responsible for talking to remote MTAs (such as at an
ISP). The remote MTA should return a too many recipients error
that your MTA sees, and that should trigger your MTA to send this
message and start a new one for the rest of the recipients.

What MTA are you using, and which ISPs are giving you this problem?
How many recipients is your MTA trying to send?

You could set SMTP_MAX_RCPTS = 1 in mm_cfg.py to force one recipient
per message. That can make a noticable difference on your bandwidth
usage though.

alex