[Dovecot] mdbox: Cannot create subfolder called "dbox-Mails" (2.0beta5)

William Blunn bill+dovecot at blunn.org
Sat Jul 3 01:37:36 EEST 2010

Timo Sirainen wrote:
> On to, 2010-05-13 at 10:14 +0100, William Blunn wrote:
>> So this means we cannot create a mail subfolder whose name is "dbox-Mails"!
> Yes. That's why it's called dbox-Mails, it's unlikely people will want to try to create it :)

You have a kind of "Special value" which has a different meaning to 
normal values.

This is sort of like a Rogue value, but in this case you cannot 
guarantee that it will always be distinct from normal legal values.

A "Special value" such as this should be carefully chosen so as to 
minimise the risk of colliding with normal values.

What about people who have e-mail relating to "postfix", "exim", and 
"dbox" and who want to file them in folders?

And what if those people are the kind of people who have the propensity 
to put the name of what a thing is within its name?

They might decide to create folders thus:


Oops. We just collided with the Special value.

The folder name 'dbox-Mails' is comprised of two normal words, and 
combined in a way which makes a relatively meaningful phrase.

As such it isn't especially unlikely, and therefore a poor choice for a 
Special value.

Compare and contrast an alternative possibility "zgo0kq2njs". This is 
the uncommon character 'z' followed by nine random alphanumeric 
characters, for a total of 10 characters, and as such should have equal 
storage complexity to the original 10 ASCII character proposal 
"dbox-Mails". But it does not make any word or phrase in any language I 
know of.

This should make a better Special value because it should be less likely 
to collide with any normal value.

For sysadminning it should be no problem. The sysadmin types "z" (or 
"zg" or perhaps "zgo") then presses TAB and completion fills in the 
rest. It seems the obscurer the better because it is less likely to have 
partial head matches with normal directory names.

One possibility would be to make the Special value for the dbox 
subdirectory be a configuration option.


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