possessives - What's the posessive form of address

What would be the correct possessive form of address? I was working on a project, and one of the error messages was

You can't spoof the address' domain

A colleague of mine pointed out that this isn't how it's supposed to be spelled, and suggested address's. That looks odd to me, so maybe it could be addresses, but that's also the plural.

Answer

Your colleague is correct.

However, if you still don't feel comfortable with it, you can get around the issue with a simple rewording:

You can't spoof the domain of the address