do the MX priorities have to be in multiples of 10?

Hello:

Traditionally, MX priorities are set in multiples of 10, and an attempt is

made to deliver the email to the server with the lowest priority first.

Do they have to be in priorities of 10, though? If an MX file has a

priority of 10, another of 9, and another of 8, will that priority "work"?

Thanks!

SQL Programmer (it's just a name)