[LINK] Bounce processing

[Tony Barry]

About a third of my email is bounces from link which majordomo sends 
to me. If an address keeps bouncing I delete it after a while 
depending on the circumstances. Remember that for every address 
bouncing I get a bounce for every message going to the list. If a 
major site falls over I get flooded. The record was 600 bounce 
message in one day.

Over the years it has got better though. The NT Government and 
Department of Finance used to regularly fail at the weekend as did 
some universities. These days it's mostly people changing their 
addresses and forgetting the list, dns trouble making the host name 
disappear eg dynamite.com.au (hi Alan and Tony), Xamax.com.au (hi 
Roger) and informa.com.au (hi Richard) , members exceeding the 
storage limit (Hi Adam - no the other one :-) and so forth.

Mailman has a way of handling this. Briefly it keeps a score of 
number of days bounces have occurred which it clears if the address 
starts to work again. If a threshold is exceeded the addresses gets 
suspended and it tries to inform the member. If it gets too bad they 
are dropped.

This is what the documentation says -

Bounce processing
These policies control the automatic bounce processing system in 
Mailman. Here's an overview of how it works.

When a bounce is received, Mailman tries to extract two pieces of 
information from the message: the address of the member the message 
was intended for, and the severity of the problem causing the bounce. 
The severity can be either hard or soft meaning either a fatal error 
occurred, or a transient error occurred. When in doubt, a hard 
severity is used.

If no member address can be extracted from the bounce, then the 
bounce is usually discarded. Otherwise, each member is assigned a 
bounce score and every time we encounter a bounce from this member we 
increment the score. Hard bounces increment by 1 while soft bounces 
increment by 0.5. We only increment the bounce score once per day, so 
even if we receive ten hard bounces from a member per day, their 
score will increase by only 1 for that day.

When a member's bounce score is greater than the bounce score 
threshold, the subscription is disabled. Once disabled, the member 
will not receive any postings from the list until their membership is 
explicitly re-enabled (either by the list administrator or the user). 
However, they will receive occasional reminders that their membership 
has been disabled, and these reminders will include information about 
how to re-enable their membership.

You can control both the number of reminders the member will receive 
and the frequency with which these reminders are sent.

There is one other important configuration variable; after a certain 
period of time -- during which no bounces from the member are 
received -- the bounce information is considered stale and discarded. 
Thus by adjusting this value, and the score threshold, you can 
control how quickly bouncing members are disabled. You should tune 
both of these to the frequency and traffic volume of your list.

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The setting I propose are -

Bounce detection sensitivity

Should Mailman perform automatic bounce processing?


	YES

The maximum member bounce score before the member's subscription is 
disabled. This value can be a floating point number.

	7
[A hard bounce for a week will disable the membership]

The number of days after which a member's bounce information is 
discarded, if no new bounces have been received in the interim. This 
value must be an integer.

	4
[No bounces for 4 days will resent the count to zero. I'm not sure if 
a shorter interval would be better]

How many Your Membership Is Disabled warnings a disabled member 
should get before their address is removed from the mailing list. Set 
to 0 to immediately remove an address from the list once their bounce 
score exceeds the threshold. This value must be an integer.

	4


The number of days between sending the Your Membership Is Disabled 
warnings. This value must be an integer.

	7
[with these settings mailman will try emailing the member four times 
at weekly intervals saying their membership is suspended]


Notifications

Should Mailman send you, the list owner, any bounce messages that 
failed to be detected by the bounce processor? Yes is recommended.
	YES

Should Mailman notify you, the list owner, when bounces cause a 
member's subscription to be disabled?

	YES

Should Mailman notify you, the list owner, when bounces cause a 
member to be unsubscribed?

	YES

Experience no doubt will show that some of these values need to change.

Tony
-- 
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phone : +61 2 6241 7659 | mailto:me@Tony-Barry.emu.id.au
mobile: +61 4 1242 0397 | http://tony-barry.emu.id.au
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