Normal users can't update their passwords (results in error)

When I create an email account on any domain for a regular user (with this I mean, NOT a system administrator) and I send them the "generated" password / information. They log into the administration part to change their password but when they actually click "update" it results in a 403 Forbidden error and the password remains unchanged.

I, on the other hand, am able to change their passwords using my system admin account.