[fetchmail-users] Re: unsafe MDA procmail recommended by fetchmail

[Thomas W. <to...@to...>]

I wrote:
> I had a "disk quota exceeded" condition here which procmail failed
> to handle properly. It accepted its input, threw it away and just
> returned success.

Stephen van den Berg wrote:
> Procmail handles quota-exceeded problems
> with flying colours since about 1993.

> There is a 99.997% probability that the serious
> issue is a user error on your part.
> ...
> In order to clarify the issue, it would be helpful
> if you can show the used procmailrc files, ...
When I did this, the issue did actually clarify (see below), ...

> Nonetheless, in order to assure timely assistance,
> it would be prudent to forward this
> information to the procmail mailinglist (instead
> of me personally), so they
> can help you fix the procmail recipe(s).
> See procmail -v as to the address of the list.
Right; I'm not doing this now because the issue has been clarified. 
Actually, it would also be prudent to add the mailing list address to 
the man page, in either the AUTHORS section or at least the -v description.


So here is the essential info:
bash> cd
bash> cat .procmailrc
MAILDIR=$HOME/Post

:0:
testbox

bash> cat testmail
From: to...@to...
To: to...@to...
Subject: test mail

1234567890123456789012345678901234567890123456789012345678901234567890

bash> if procmail -p < testmail ; then echo y ; fi
procmail: Quota exceeded while writing "testbox"
y
bash> ls -l Post/testbox 
-rw-------   1 demsn702 mdd            0 Nov  2 17:08 Post/testbox
bash> cat /tmp/procmail.log.
procmail: Quota exceeded while writing "testbox"
procmail: Truncated file to former size
 Subject: test mail
  Folder: /var/mail/....                                                 1266
bash> 


At this point, I noticed that procmail has a fallback behaviour 
that when delivery to a local folder fails, it delivers into 
/var/mail instead. So actually the mail was not lost.
This is, however, not documented anywhere. It is very unexpected 
behaviour for a user who has a configuration file that refers only 
to local folders (for mail sorting, spam filtering, etc). After all, 
if I configure local folders, I'm doing it just because I do not 
intend (or cannot) use /var/mail.
The event that procmail redirects into the system mailbox due to 
a failure should be noted clearly to the user in this case (on 
stdout/stderr, as well as in the logfile folder).

So, quoting you again
> There is a 99.997% probability that the serious
> issue is a user error on your part.
I would not say this issue was a user error on my part (because it's 
not properly documented), but it's not a serious issue as I said 
before. Procmail handles an inaccessible system mailbox well (this is 
documented); I was not able to check what would happen if /var/mail is 
completely inaccessible but I assume something reasonable should 
happen too, so I withdraw my statement that procmail is an unsafe MDA.

User feedback and documentation should be improved, though, and maybe 
this case of redirection should not be applied at all (or be configurable) 
and rather a proper error indication returned instead.

Thanks and kind regards,
Thomas Wolff