[Mailman-Users] Bounce Processing and User Notifications

Mark Sapiro mark at msapiro.net
Thu Jul 1 06:26:47 CEST 2010

Ian Prietz wrote:
>We have a Mailman service that is hosted. I previously asked a question re: Bounce notifications. Mark indirectly suggested that I change my bounce processing score to <=1. I think what I am going to do for initial testing is set the bounce score to .5. That way I will be notified of pretty much any instance that something comes up.
>Then after kinks get worked out, I can raise it to 1, so then I am only notified of hard bounces.
>1. Does that sound like a good idea or a good place to start?

Actually, documentation notwithstanding, Mailman doesn't distinguish
hard and soft bounces for scoring purposes. Bounces are considered
permanent or temporary based on how they are reported in the DSN. For
an RFC 3464 compliant DSN, a bounce is scored 1 point if it's action
starts with 'fail' and 0 otherwise.

For errors reported directly during Mailman's SMTP, a 5xx status is a
bounce, and a 4xx status is retried.

>2. Would a hard bounce be something from a server like "Undeliverable due to File Attachment Limit exceeded" or "Unknown User"?

Anything that says the message wasn't delivered is a score = 1 bounce
(if it is recognized).

>3. What type of bounce would a "Too many recipients as this time" or "Delivery Delay" messages be? Soft or Hard?

Generally, 'delay' type DSNs are ignored by Mailman and not considered
bounces at all.

>4. Is there a way to keep a subscriber from being notified when their account is disabled? Like should I set the Membership Disabled message to 0 so they are just removed and I am notified that way? I am trying to do as much behind the scenes without them being notified and worrying about what happened.

You can set bounce_you_are_disabled_warnings to 0 and set
send_goodbye_message to no, but consider that if the address is truly
undeliverable, the user won't receive any notices anyway, and if not,
you might want them to know there is a problem.

>5. How can I simulate a bounce to test this out. I tried adding a bogus email address from our domain to the list, and it seemed to make delivery to the other recipients take longer, and I don't remember that email address' bounce score raising any higher. I at least expected to get a "User does not exist" message.

That depends in part on your MTA. Also, what is a bogus email address?
If you want a truly bogus address, see RFC 2606. I suggest
user at xxx.invalid.

Assuming the domain is truly non-existent, the MTA may verify it during
SMTP with Mailman and return either a 4xx or 5xx status depending on
MTA configuration (domain verification during SMTP with Mailman is not
recommended for performance reasons). In this case, a 5xx status will
be scored as a bounce and a 4xx status will be retried by Mailman at
(default) 1 hour intervals for (default) 5 days after which Mailman
just gives up and does not score it as a bounce.

>As I said before, I want to be notified of any problems to begin with to see if I need to contact any administrators in case our domain is blocked. And then, once these kinks have been worked out, I would like to just receive FAILURES or ERRORS.

Basically, anything that results in the message not being delivered
(except endless retry of 4xx SMTP status) will result in a bounce. If
you want to see every such bounce, you need to be sure that at least
bounce_unrecognized_goes_to_list_owner and
bounce_notify_owner_on_disable are set to Yes and
bounce_score_threshold is <= 1.0.

As I said, as far as Mailman is concerned pretty much anything that
results in a 'bounce' is a FAILURE or ERROR. DSNs which say
effectively "I haven't delivered your mail yet, but I'm still trying"
or DSNs which say "I successfully delivered your mail" (if any MTA
actually sends those) are ignored. Anything else says "I didn't
deliver your mail" and is a bounce scored as 1.0, regardless of
whether it says "the address is totally non-existent" or "the mailbox
was over quota" or "the receiving MX was off line" or any other reason.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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