[Qt-interest] Delayed message delivery from this list

[Konrad Rosenbaum]

On Monday 14 March 2011, Sean Harmer wrote:
> Am I the only person seeing some messages being delayed by several hours
> before delivery from this list?

No.

> This has been happening on and off for the last week or two. The messages
> show up immediately in the list archives but delivery happens some hours
> later.

This is because it is stored in the archive immediately upon receipt and 
then scheduled for delivery. Normally mailman schedules mails in batches of 
5 or more recipients. 

What then happens depends on the mail transport agent (MTA, in this case 
Postfix). For most MTAs: if any one of the recipients of a mail is delayed, 
the whole batch gets delayed - so if you happen to be behind a mail 
recipient that has some kind of delay (greylisting, server down, etc.) that 
you get delayed together with that recipient.

Don't worry: if a recipient cannot be reached permanently then it is dropped 
and the mail delivered to the remainder of the batch.

> Messages from this list used to arrive within a few minutes of being sent
> to the list - I think mailman cronjobs are usually set to run at 5
> minute intervals so that would seem reasonable.

It all depends on random chance and batching...

It all comes down to some fine tuning:

Smaller batches mean faster delivery and less chance of a blocking 
recipient.

Bigger batches mean (significantly) less load on the mail server.

So you can petition the mailman-admins to configure smaller batches, but 
they may object on the grounds of server load.



	Konrad
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