Hello.

I have a customer who is currently using AD FS for internal claims aware applications and some SaaS applications. They are using AD FS 2012 R2. Federation server address: ADFS.contoso.net 

The customer will also start to federate with O365 applications via the same AD FS instance they are currently using. The customer will be using AltLogoinID feature within AD FS and will use the "mail" attribute to supplement UPN

I'm looking some info about impact to existing trusts when they integrate the existing ADFS with O365. Lessons learned, Do's & Dont's, etc?

Thanks