[SOLVED]Dovecot not allowing new IMAP folders

Recently I decided to rebuild my Linode and reconfigure everything from scratch. Prior to this, Dovecot allowed me to create and delete folders over IMAP on all three of my domains, however now it does not allow new folders for one of them. Strangely, the domain that cannot create folders has the subdomain used as the MX record for all three.

The mail server was configured exactly the same both before and after the rebuild, using this Linode Library guide on Debian Wheezy.

I'll soon require a working mailserver, so suggestions would be greatly appreciated.

Edit: The other two domains can create folders over IMAP.