Mailbox Account Creation Error

In Virtualmin Professional 3.30, when attempting to create a new mailbox account for an existing virtual server, I am getting the following error:

Failed to save mailbox : Password contains or is the same as username

This is a simple e-mail account creation with a normal username (no numbers or symbols) and a random password (which is the default on my system). I have tried it a few times with different passwords, and they have no relation to the username, but the error still appears.

Status: 
Closed (fixed)