[Dovecot] resilience suggestion

[David Lee]

On Fri, 9 Feb 2007, Jakob Hirsch wrote:

> Quoting David Lee:
>
> > We have had a source code hack since October (in "deliver.c", simply
> > replacing a "return ret" occurence with "return EX_TEMPFAIL") and it has
>
> I cannot speak for Timo, but if this means mail for non-existing users
> will stay in the MTA's queue until it times out, it's definitely wrong.

It may, indeed, be wrong for many sites.  But that's why I had also said:
   "option ... if the circumstances were appropriate for the site"

However, at many _other_ sites, the outlying email infrastructure may
ensure that only email for existing users gets anywhere near the dovecot
machine in the first place.  That is, by the time the email gets to
"deliver", one is 99.99% certain that the user is a valid, existing one.
(Furthermore, routine monitoring of the MTA queue can draw the sys.admin's
attention to any email (should usually be close to zero at such sites)
that has been sitting there for too long... a problem of some sort which
requires attention anyway... and by my proposed "EX_TEMPFAIL" at least
this possibly valid email has not been rejected.)


> Apart from that, nscd is one of the first things I remove from freshly
> installed systems, because it's plain crap and caused only problems in
> the past. Even though I can hardly believe they do not get even such
> things right.

Agreed!!  But we have a totally different PAM authentication problem (way
outside email protocols) in the FC series which seems to require us to
have "nscd" positively running.  (Grumble).  We're addressing that, too.

Meanwhile, for some sites, in some circumstances, "return EX_TEMPFAIL" may
be more appropriate than a "5xx", to have available as an option.

Hope that helps.


-- 

:  David Lee                                I.T. Service          :
:  Senior Systems Programmer                Computer Centre       :
:  UNIX Team Leader                         Durham University     :
:                                           South Road            :
:  http://www.dur.ac.uk/t.d.lee/            Durham DH1 3LE        :
:  Phone: +44 191 334 2752                  U.K.                  :