Re: [exim] Using Routing, Maildir and MBOX for email backups

Phil Pennock wrote:
> On 2009-06-10 at 09:55 -0700, David Chait wrote:
> [ Mike Cardwell wrote: ]
>>> That sounds fine to me. However, one recommendation I'd make is to use
>>> maildir for the backup as well as the live mail instead of mbox. That
>>> way you can easily delete mail from your backup over a certain age. Eg,
>>> to delete everything over 30 days (untested):
>
>> It really depends on the mail server in question, cyrus-imap would break
>> if you simply deleted the file as the folder indexes would become out of
>> sync.
>
> Mike said maildir. Cyrus does not use Maildir. They are different
> storage formats.

ACK. Aware of that here. We've used 'em side-by-side for ages.

JMNSHO, but while Cyrus has its pluses - AFAICS it needs a bit higher level of
groking than maildirs to use well. Tried it twice, went away confused.

>
> There is a similarity in that there is one file per email and the
> content of the files is fairly similar, since it's the natural format.
> That's about as far as the similarities go.
>
> Maildir has three sub-directories under the directory corresponding to a
> folder, "cur/", "new/" and "tmp/" if memory serves, and procedures for
> how mail is created and moved around using those directories, such that
> the locking is moved into the filesystem metadata which has good sides
> and bad sides, depending upon scale and architecture. It scales well
> enough for many people. Sub-folders use directory names starting with a
> dot, IIRC.
>

Good explanation. The 'dot', BTW, while in both the Maildir & Maildir+ usage, is
not an absolute requirement for Dovecot, and one of the things we like about
that IMAPD. Not having to always deal with dots makes it easier to use links to
create and tear-down 'bespoke' shared folder structures for team-working,
project-working, management oversight et al.

> Cyrus uses a format where the directory which is the mail-folder names
> the emails "1.", "2.", etc and uses files starting "cyrus." for things
> like indices, caches, full body search corpora, etc and maintains
> per-user read state in a separate area entirely. Sub-folders are just
> directories with the same name, IIRC.
>
> With Maildir, if you have the mail and know which directory it came
> from, you have the backup.

..and grep can find it and lynx or links can confirm it. Easy navigation in
Maildir, less-so otherwise.

> With Cyrus's storage format, you don't.

ACK. potential RPITA. (R as in 'Royal')

> Maildir is intended to be an open format,

Dunno for sure what DB 'intended'.. but with Sam and many others piling-on, it
has certainly became one. Works 'well enough' all around, too, though we still
like mbox for read-only-and-damn-seldom-at-that MLM digests or 'deep' archives.

> used by multiple pieces of
> software, whereas Cyrus's storage is an internal implementation detail.
>
> All that said, I use Cyrus. But Mike's assertion of Maildir behaviour
> is not invalidated by anything Cyrus does differently.
> -Phil
>

ACK.

Also 'for posterity' many of us go to greate lengths to agonize over which to
use on the *server*

- then sit with a choice from any of several dozen MUA's - where far more of our
messages may accumulate over time

- that use (modified) mbox monoliths and-no-other-choice anyway.

Guilty as charged - SeaMonkey MUA here. OTOH, it doesn't seem to break, even
with several years worth of lists like this one in local store.

Cheers,

Bill