Re: Mail Server Problem

[Brian Candler <B.Candler at pobox.com>]

On Sun, Dec 29, 2002 at 04:51:50PM +0000, Mensah Komla Agbessitse wrote:
>    This is the output of the command which actually reveal what you
>    mentioned.
> 
>    # fstyp -v /dev/dsk/c0t9d0s7 | head -20
...
>    nbfree  0       ndir    43223   nifree  949097  nffree  4061748

That's it then - no free blocks, only fragments remaining, so unable to
create any large files.

Sorry but all I can suggest is you treat this the same as a full filesystem:
that is, add some more disks as another volume and move some accounts there,
and/or look for unneeded files and delete them. If there are non mailbox
items on this partition, such as log files or spool files, then move them to
a different one (if this other partition is a different physical disk then
it may improve performance too)

It might be possible to reformat the filesystem with a smaller bsize (you'll
need to ask someone else how to do that - my knowledge of Solaris is
minimal) but in any case that would end up destroying all the data of
course. Disks are relatively cheap, good disk shelves less so; if you can
install more disks, that would be the way to go.

Apart from that, do you have a mail ageing policy? Do you have a lot of
inactive accounts which are just sitting there collecting spam? This is a
common problem in my part of the world, where "free" Internet accounts are
the norm, so many people create accounts and then just leave them when they
have had enough - but they still sit there receiving spam.

A mail ageing policy needs to be designed carefully so as not to upset your
users, especially if they are paying. However if you have complete and
accurate logs of when people last accessed their mailbox, you can implement
a policy like this:

1. if a mailbox has not been accessed for X days, then all subsequent
   incoming mail for that account is bounced ("550 Mailbox inactive")
   without deleting any stored mail. If they start using it again then
   you start accepting further mail again.
2. if a mailbox has not been accessed for Y days, then delete all stored
   messages which it contains
3. if an account has not been used for Z days, then delete the mailbox and
   purge it entirely from your database (applies only to free accounts
   obviously)

Step (1) needs some careful log processing, and flagging the user in your
database as 'inactive'. Doing this is very implementation-specific. I have
used Exim with an extra LDAP attribute which is checked in a router (marked
as verify_only) - this lets Exim bounce the address at RCPT TO time, without
having to queue and then attempt to return the mail to sender, which almost
always fails anyway because spam invariably has a false return address.

Values of X/Y/Z depend on how drastic you want to be with your customers: I
would suggest 30/60/90 as the minimum and 60/180/365 as generous.

Regards,

Brian.

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