Re: [Fetchmail-users] fetchmail expunge error

[Alan D. S. <sal...@at...>]

On 2021-04-26 19:31:23, Matthias Andree <mat...@gm...> spake thus:
>Am 26.04.21 um 14:46 schrieb Leslie Rhorer:
>>
>> On 4/25/2021 9:15 PM, Alan D. Salewski wrote:
[...]

>>> Yes, the below fetchmail config line is what I use to pull mail from
>>> AT&T via
>>> POP3, but I am doing it from 'inbound.att.net':
>>>
>>>     poll inbound.att.net port 995 protocol pop3 timeout 120 uidl
>>> username "my-...@at..." ssl sslcertck password
>>> "MY-SECURE-MAIL-KEY-VALUE" expunge 10 fetchall
>>>
>>     Yep, you bet.  Thanks!  I am not even using the "expunge" verb,
>> and it still seems to work so far.
>
>Just to shed some light on this expunging:

[ All good stuff related to protocol-level DELE/QUIT, EXPUNGE/CLOSE. ]

Since we're talking about it, though, I'll note that in the particular config
above, the 'expunge 10' clause is primarily serving as a throttle for message
delivery to the local MTA. It is a minor abuse of the 'expunge' "end the
session" behavior documented in fetchmail(1) for POP2 and POP3:

        -e <count> | --expunge <count>
               (Keyword: expunge)
               Arrange  for  deletions to be made final after a given number of
               messages.  Under POP2 or POP3, fetchmail cannot  make  deletions
               final  without  sending QUIT and ending the session -- with this
               option on, fetchmail will break a long  mail  retrieval  session
               into multiple sub-sessions, sending QUIT after each sub-session.
               ...

I say "minor abuse" because the feature is documented as a tool to help cope
with flakey connections to the maildrop server, which is not the intent of my
use.

The local MTA happens to be configured to only attempt immediate delivery of
up to ten messages from a given SMTP session (the rest get queued for later
delivery whenever the mail queue delivery runner wakes up to do its
thing). The effect of using the 'expunge 10' clause is that fetchmail will
only hand off ten messages at a time to the local MTA, so all will enjoy
immediate delivery (since fetchmail only attempts delivery within the ten
message limit).  However, a (hypothetical) runaway process on the machine
attempting to send out a gazillion email messages all at once would land (
gazillion minus ten ) messages in the mail queue (hopefully with enough time
for somebody to notice and purge them before attempting delivery either
locally or remote).

-Al

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