F5 APM and Exchange 2013 with multiple domains for authentification

Just curious, but do you have a branch condition like this?

expr { [mcget {session.logon.last.domain}] equals "ad.groupe.net" }        

I'd also throw in a test message box directly after the logon page to see what your domain variable is before it gets to the domain check agent. Use this syntax in the message box field:

%{session.logon.last.domain}