How can I remove the restriction for passwords for email accounts?

I'm moving my email service from another server to dynu and I want to continue using the existing passwords (which don't contain special characters, etc).

Thanks,
John

Nevermind ... I wanted to get things going and so opted to change my passwords. But, I would like the option to set whatever password I would like on *my* email accounts in *my* own domain in the future. ;) Thanks very much.