[Dovecot] Dovecot LDA and address extensions - folders flood

[huret deffgok]

Hi list,

This post is slightly OT, I hope no one will take offense.
I was following the wiki on using dovecot LDA with postfix and implemented,
for our future mail server, the address extensions mechanism: an email sent
to "validUser+foldername at mydomain.com" will have dovecot-lda automagically
create and subscribe the "foldername" folder. With some basic scripting I
was able to create hundreds of folders in a few seconds. So my question is
how do you implement this great feature in a secure way so that funny
random people out there cant flood your mailbox with gigatons of folder.

Thanks,
kfx