[Dovecot] Using MySQL to store email?

[Marc Perkel]

Les Mikesell wrote:
> I think the people who expect an improvement from databases over maildir
> are used to unix filesystems that degrade badly as the number of files
> in a directory increase.  These days many, like Reiserfs and XFS, are
> much better.  My theory is that if your filesystem isn't a good place
> to store things you should fix that before thinking about databases.
>
>   

Suppose you have a total of one million messages stored for 5000 users 
across 800 domains and you want to delete all message that were sent 
from a specific host. With MySQL it's a one line command and would take 
only a few seconds to execute. Using Maildir it would take hours because 
you would have to search every message. That's the power of MySQL.

Maildir only is fast for indexing file names. But if you are indexing 
across users and domains by host, or headers, or senders, or whatever 
then only a database can support these multiple indexes. There are 
things you can do with databases that are way beyond what you can 
imagine. Especially if you are integrating it with a spam system.

For example, a new message comes in and you find that sender matches 
email in 100 people's spam folders and none in any other folder? It can 
be classified as spam. If however the from address matches ham in people 
folder and no spam then you can probably deliver it without spam scanning.

This issue isn't performance, it's power. If you compare it with what 
people are doing now then MySQL would probably be a little slower. But 
if you compare it to what is possible that you can't do now then MySQL wins.