[Mailman-Users] Mailman + Postfix - Too Many Connections

Jaco Kroon jaco at kroon.co.za
Thu May 7 11:15:29 CEST 2009

Alice Kaerast wrote:
> On Thu, 07 May 2009 15:42:45 +1000
> "Lie, Jafaruddin" <lie at acer.edu.au> wrote:
>> This is not strictly a mailman issue, but I would assume some people
>> here would have encountered this issue.
>> We sent out mailing lists to schools here in Australia, and recently
>> we've been getting "Too Many Connections #421" errors from them.
>> Mails destined to gmail or hotmail are OK.
>> We're not trying to spam them (we have put links to unsubscribe, etc)
>> but since the same mail server hosts emails for almost all the school
>> domains, it's not liking us. I've set postfix variable of
>> default_destination_recipient_limit to 15, still not liking it.
>> Any suggestions on rate-limiting on Postfix / mailman??

Try working around this when your upstream gives 550 errors for rate 
limiting :p.

Anyway, the way to do concurrency limiting on exim (just so we have it 
in the archives) is to add serialize=* in your transport.  rate limiting 
isn't that easy and waiting for the 4xx error is probably the easiest, 
just set your retry rules to retry every 15 minutes continually.

Either way, Too Many Connections sounds like concurrency to me, not rate 


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