[Mailman-Developers] [Mailman-checkins] SF.net SVN: mailman: [8041] trunk/mailman/Mailman

[Brad Knowles]

At 3:04 PM -0400 9/27/06, Barry Warsaw wrote:

>  This appears to allow us to set up true virtual domains without
>  having to encode destination aliases.  The trick though is that we
>  would use Maildir delivery for all incoming messages, something I'm
>  keen on switching to for Mailman 2.2 anyway.  Maildir is way more
>  efficient than invoking a mail program per incoming message, Mailman
>  already supports Maildir (although it isn't the default), and AFAIK
>  all major MTAs support Maildir.

Sendmail knows nothing of the mailbox delivery method.  That is left 
up to the Local Delivery Agent, which is usually /bin/mail and knows 
about 7th edition mbox-format, and not much else.  You could always 
substitute a different LDA (e.g., procmail), but that would not be a 
standard part of sendmail.

Moreover, I'm not keen on Maildir.  It makes a lot of trade-offs to 
try to get something that is NFS-safe, and I'm not convinced those 
trade-offs are worthwhile, especially not in a non-NFS environment. 
I think there are other ways that you could get the same benefits (in 
a mailbox directory solution), without getting the major drawbacks of 
Maildir per se.


Among other things Maildir creates really hairy long filenames, which 
can easily blow the iname/inode caching built into most filesystems 
-- you could get the same benefit by using a better filename 
naming/hashing scheme with fewer characters.  It also does a lot of 
excessive synchronous meta-data operations (e.g., creating files, 
renaming files, etc...), and that can place a heavy load on the 
underlying filesystem.

In his paper regarding what they built for the Earthlinnk mail 
system, Nick Christenson has clearly proven that you can use the 
atomic creat() system call in a way that eliminates the need for file 
locking on NFS, without all the various baggage that Maildir brings 
to the table.

Mark Crispin also has a lot of good things to say about the 
weaknesses inherent in Maildir.  You should read his comments, too.

-- 
Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

  Founding Individual Sponsor of LOPSA.  See <http://www.lopsa.org/>.