I think that this is nothing we should bother about. This is not one of our top ten problems, and we risk creating accidental implementation problems. Little details that turn out to be difficult to achieve. Here is an example: You may remember how marksv mentioned that adding EAI addresses is difficult because of integration. Office365 addresses are bound to Skype etc via the auth backend (details probably are different). If we say "addresses should do x" and Skype cannot do x, Microsoft has a problem which requires meetings and attention and general resources to resolve. Even if we say "it is a little advisable", one of Mark's less intelligent colleagues will miss the subtlety, raise the issue and it takes time. The same applies at other companies, expect that the compatibility problem is some other legacy code. The correct optimisation for us is to weigh simplicity of implementation heavier than everything else. IMO. Arnt